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{{Short description|US naval inventory classification system}}
{{About|the U.S. Navy, U.S. Coast Guard, and NOAA systems|the similar system used by Canadian Forces|Hull classification symbol (Canada)}}
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{{United States Navy ship types}}

The [[United States Navy]], [[United States Coast Guard]], and United States [[National Oceanic and Atmospheric Administration]] (NOAA) use a '''hull classification symbol''' (sometimes called '''hull code''' or '''[[hull number]]''') to identify their ships by type and by individual ship within a type. The system is analogous to the [[pennant number]] system that the [[Royal Navy]] and other European and [[Commonwealth of Nations|Commonwealth]] navies use.

== History ==

=== United States Navy ===
The U.S. Navy began to assign unique [[Naval Registry Identification Number]]s to its ships in the 1890s. The system was a simple one in which each ship received a number which was appended to its ship type, fully spelled out, and added parenthetically after the ship's name when deemed necessary to avoid confusion between ships. Under this system, for example, the [[battleship]] [[USS Indiana (BB-1)|''Indiana'']] was USS ''Indiana'' (Battleship No. 1), the [[cruiser]] [[USS Olympia (C-6)|''Olympia'']] was USS ''Olympia'' (Cruiser No. 6), and so on. Beginning in 1907, some ships also were referred to alternatively by single-letter or three-letter codes—for example, USS ''Indiana'' (Battleship No. 1) could be referred to as USS ''Indiana'' (B-1) and USS ''Olympia'' (Cruiser No. 6) could also be referred to as USS ''Olympia'' (C-6), while USS ''Pennsylvania'' (Armored Cruiser No. 4) could be referred to as USS ''Pennsylvania'' (ACR-4). However, rather than replacing it, these codes coexisted and were used interchangeably with the older system until the modern system was instituted on 17 July 1920.<ref name=DerDigiCru1/>

During [[World War I]], the U.S. Navy acquired large numbers of privately owned and commercial ships and craft for use as [[patrol vessel]]s, [[Minelayer|mine warfare vessels]], and various types of naval [[auxiliary ship]]s, some of them with identical names. To keep track of them all, the Navy assigned unique identifying numbers to them. Those deemed appropriate for patrol work received [[section patrol]] numbers (SP), while those intended for other purposes received "identification numbers", generally abbreviated "Id. No." or "ID;" some ships and craft changed from an SP to an ID number or vice versa during their careers, without their unique numbers themselves changing, and some ships and craft assigned numbers in anticipation of naval service were never acquired by the Navy. The SP/ID numbering sequence was unified and continuous, with no SP number repeated in the ID series or vice versa so that there could not be, for example, both an "SP-435" and an "Id. No. 435". The SP and ID numbers were used parenthetically after each boat's or ship's name to identify it; although this system pre-dated the modern hull classification system and its numbers were not referred to at the time as "hull codes" or "hull numbers," it was used in a similar manner to today's system and can be considered its precursor.<ref>Naval History and heritage Command Online Library of Selected Images (archived from [https://web.archive.org/web/20031007233309/http://www.history.navy.mil/photos/shusn-no/spid-no.htm the original] at https://web.archive.org/web/20100329212007/http://www.history.navy.mil/photos/shusn-no/spid-no.htm).</ref>

=== United States Revenue Cutter Service and United States Coast Guard ===
The [[United States Revenue Cutter Service]], which merged with the [[United States Lifesaving Service]] in January 1915 to form the modern [[United States Coast Guard]], began following the Navy's lead in the 1890s, with its [[United States Coast Guard Cutter|cutters]] having parenthetical numbers called [[Naval Registry Identification Number]]s following their names, such as (Cutter No. 1), etc. This persisted until the Navy's modern hull classification system's introduction in 1920, which included Coast Guard ships and craft.

=== United States Coast and Geodetic Survey ===

Like the U.S. Navy, the [[United States Coast and Geodetic Survey]] – a uniformed seagoing service of the [[United States Government]] and a predecessor of the [[National Oceanic and Atmospheric Administration]] (NOAA) – adopted a hull number system for its fleet in the 20th century. Its largest vessels, "Category I" [[Oceanography|oceanographic]] [[survey ship]]s, were classified as "ocean survey ships" and given the designation "OSS". Intermediate-sized "Category II" oceanographic survey ships received the designation "MSS" for "medium survey ship," and smaller "Category III" oceanographic survey ships were given the classification "CSS" for "coastal survey ship." A fourth designation, "ASV" for "auxiliary survey vessel," included even smaller vessels. In each case, a particular ship received a unique designation based on its classification and a unique hull number separated by a space rather than a hyphen; for example, the third Coast and Geodetic Survey ship named ''Pioneer'' was an ocean survey ship officially known as [[USC&GS Pioneer (OSS 31)|USC&GS ''Pioneer'' (OSS 31)]].<ref>[https://books.google.com/books?id=uYSPAAAAMAAJ&dq=Ocean+Survey+Ship+%28OSS%29+MSS+CSS&pg=PA3612 United States Department of State, ''United States Treaties and Other International Obligations, Volume 23, Part Four'', Washington, D.C.:U.S. Government Printing Office, 1972, p. 3612.]</ref><ref>{{Cite web |url=http://docs.lib.noaa.gov/rescue/cgs/011_pdf/CSC-0205.pdf |title=United States Department of Commerce, ''Annual Report of the Director of the Coast and Geodetic Survey for the Fiscal Year Ending June 30, 1964'', U.S. Government Printing Office, Washington, D.C.: 1964, pp. 3–5. |access-date=6 May 2014 |archive-url=https://web.archive.org/web/20130219015620/http://docs.lib.noaa.gov/rescue/cgs/011_pdf/CSC-0205.pdf |archive-date=19 February 2013 |url-status=dead }}</ref> The Coast and Geodetic Survey{{'}}s system persisted after the creation of NOAA in 1970, when NOAA took control of the Survey{{'}}s fleet, but NOAA later changed to its modern hull classification system.

=== United States Fish and Wildlife Service ===

The Fish and Wildlife Service, created in 1940 and reorganized as the [[United States Fish and Wildlife Service]] (USFWS) in 1956, adopted a hull number system for its [[Fisheries science|fisheries]] [[research ship]]s and [[patrol vessel]]s. It consisted of "FWS" followed by a unique identifying number. In 1970, NOAA took control of the seagoing ships of the USFWS's Bureau of Commercial Fisheries, and as part of the NOAA fleet they were assigned new hull numbers beginning with "FRV," for Fisheries Research Vessel, followed by a unique identifying number. They eventually were renumbered under the modern NOAA hull number system.

== The modern hull classification system ==

=== United States Navy ===

The U.S. Navy instituted its modern hull classification system on 17 July 1920, doing away with section patrol numbers, "identification numbers", and the other numbering systems described above. In the new system, all hull classification symbols are at least two letters; for basic types the symbol is the first letter of the type name, doubled, except for aircraft carriers.

The combination of symbol and hull number identifies a modern Navy ship uniquely. A heavily modified or re-purposed ship may receive a new symbol, and either retain the hull number or receive a new one. For example, the heavy gun cruiser {{USS|Boston|CA-69}} was converted to a gun/missile cruiser, changing the hull number to CAG-1. Also, the system of symbols has changed a number of times both since it was introduced in 1907 and since the modern system was instituted in 1920, so ships' symbols sometimes change without anything being done to the physical ship.<ref>Derdall and DiGiulian, (section: ''Nomenclature history'')</ref>

Hull numbers are assigned by classification. Duplication between, but not within, classifications is permitted. Hence, CV-1 was the [[aircraft carrier]] {{USS|Langley|CV-1|6}} and BB-1 was the battleship {{USS|Indiana|BB-1|6}}.

Ship types and classifications have come and gone over the years, and many of the symbols listed below are not presently in use. The [[Naval Vessel Register]] maintains an online database of U.S. Navy ships showing which symbols are presently in use.

After [[World War II]] until 1975, the U.S. Navy defined a "[[frigate]]" as a type of surface warship larger than a [[destroyer]] and smaller than a cruiser. In other navies, such a ship generally was referred to as a "[[flotilla leader]]", or "destroyer leader". Hence the U.S. Navy's use of "DL" for "frigate" prior to 1975, while "frigates" in other navies were smaller than destroyers and more like what the U.S. Navy termed a "[[destroyer escort]]", "[[ocean escort]]", or "DE". The [[United States Navy 1975 ship reclassification]] of [[cruiser]]s, frigates, and ocean escorts brought U.S. Navy classifications into line with other nations' classifications, at least cosmetically in terms of terminology, and eliminated the perceived [[United States Navy 1975 ship reclassification#The "cruiser gap"|"cruiser gap"]] with the [[Soviet Navy]] by redesignating the former "frigates" as "cruisers".

==== Military Sealift Command ====
If a U.S. Navy ship's hull classification symbol begins with "T-", it is part of the [[Military Sealift Command]], has a primarily civilian crew, and is a [[United States Naval Ship]] (USNS) in non-commissioned service – as opposed to a [[Ship commissioning|commissioned]] [[United States Ship]] (USS) with an all-military crew.

=== United States Coast Guard ===
If a ship's hull classification symbol begins with "W", it is a commissioned [[United States Coast Guard Cutter|cutter]] of the [[United States Coast Guard]]. Until 1965, the Coast Guard used U.S. Navy hull classification codes, prepending a "W" to their beginning. In 1965, it retired some of the less mission-appropriate Navy-based classifications and developed new ones of its own, most notably WHEC for "[[high endurance cutter]]" and WMEC for "[[medium endurance cutter]]".

=== National Oceanic and Atmospheric Administration ===
The [[National Oceanic and Atmospheric Administration]] (NOAA), a component of the [[United States Department of Commerce]], includes the [[National Oceanic and Atmospheric Administration Commissioned Officer Corps]] (or "NOAA Corps"), one of the eight [[uniformed services of the United States]], and operates a fleet of seagoing research and survey ships. The [[NOAA ships and aircraft|NOAA fleet]] also uses a hull classification symbol system, which it also calls "hull numbers," for its ships.

After NOAA took over the former fleets of the U.S. Coast and Geodetic Survey and the U.S. Fish and Wildlife Service Bureau of Commercial Fisheries in 1970, it initially retained the Coast and Geodetic Survey's hull-number designations for its [[survey ship]]s and adopted hull numbers beginning with "FRV", for "Fisheries Research Vessel", for its [[Fishery|fisheries]] [[research ship]]s. It later adopted a new system of ship classification, which it still uses today. In its modern system, the NOAA fleet is divided into two broad categories, research ships and survey ships. The research ships, which include [[Oceanography|oceanographic]] and fisheries research vessels, are given hull numbers beginning with "R", while the survey ships, generally [[hydrography|hydrographic]] survey vessels, receive hull numbers beginning with "S". The letter is followed by a three-digit number; the first digit indicates the NOAA "class" (i.e., size) of the vessel, which NOAA assigns based on the ship's [[gross tonnage]] and [[horsepower]], while the next two digits combine with the first digit to create a unique three-digit identifying number for the ship.

Generally, each NOAA hull number is written with a space between the letter and the three-digit number, as in, for example, {{ship|NOAAS|Nancy Foster|R 352}} or {{ship|NOAAS|Thomas Jefferson|S 222}}.<ref>Wertheim, ''The Naval Institute Guide to Combat Fleets of the World, 15th Edition: Their Ships, Aircraft, and Systems'', p. 1005.</ref>

Unlike in the U.S. Navy system, once an older NOAA ship leaves service, a newer one can be given the same hull number; for example, "S 222" was assigned to {{ship|NOAAS|Mount Mitchell|S 222}}, then assigned to NOAAS ''Thomas Jefferson'' (S 222), which entered NOAA service after ''Mount Mitchell'' was stricken.

== United States Navy hull classification codes ==

The U.S. Navy's system of alpha-numeric ship designators, and its associated hull numbers, have been for several decades a unique method of categorizing ships of all types: combatants, auxiliaries and district craft. Although considerably changed in detail and expanded over the years, this system remains essentially the same as when formally implemented in 1920. It is a very useful tool for organizing and keeping track of naval vessels, and also provides the basis for the identification numbers painted on the bows (and frequently the sterns) of most U.S. Navy ships.

The ship designator and hull number system's roots extend back to the late 1880s when ship type serial numbers were assigned to most of the new-construction warships of the emerging "Steel Navy". During the course of the next thirty years, these same numbers were combined with filing codes used by the Navy's clerks to create an informal version of the system that was put in place in 1920. Limited usage of ship numbers goes back even earlier, most notably to the "Jeffersonian Gunboats" of the early 1800s and the "Tinclad" river gunboats of the Civil War Mississippi Squadron.

It is important to understand that hull number-letter prefixes are not acronyms, and should not be carelessly treated as abbreviations of ship type classifications. Thus, "DD" does not stand for anything more than "Destroyer". "SS" simply means "Submarine". And "FF" is the post-1975 type code for "Frigate."<ref>{{cite web|title=U.S. Navy Ships – Listed by Hull Number|url=http://www.history.navy.mil/photos/shusn-no/usnsh-no.htm|archive-url=https://web.archive.org/web/20021022171348/http://www.history.navy.mil/photos/shusn-no/usnsh-no.htm|url-status=dead|archive-date=22 October 2002|publisher=Naval History and Heritage Command}}</ref>

The hull classification codes for ships in active duty in the United States Navy are governed under Secretary of the Navy Instruction 5030.8D.<ref>[https://web.archive.org/web/20221121223223/https://www.nvr.navy.mil/5030.8D.pdf SECNAVINST 5030.8D]</ref>

=== Warships ===
Warships are designed to participate in combat operations.

The origin of the two-letter code derives from the need to distinguish various cruiser subtypes.<ref name=DerDigiCru1>Derdall and DiGiulian, (section: ''Cruisers'')</ref>
{| class="wikitable"
|-
| Battleship
| Heavy gun-armed vessel (–1962)
! BB
|-
|align="center" rowspan="5" | Cruiser
| armored (1921–1931)<br>heavy (1931–1975)
! CA
|-
| large (–1947)
! CB
|-
| battle<br/>command<br/>(–1961)
! CC
|-
| light (–1950)
! CL
|-
| aviation or ''voler''
! CV
|-
|align="center" rowspan="2" | Destroyer
| ship
! DD
|-
| escort
! DE
|}

==== Aircraft carrier type ====
Aircraft carriers are ships designed primarily for the purpose of conducting combat operations by aircraft which engage in attacks against airborne, surface, sub-surface and shore targets. Contrary to popular belief, the "CV" hull classification symbol does not stand for "carrier vessel". "CV" derives from the cruiser designation, with one popular theory that the V comes from French ''voler'', "to fly", but this has never been definitively proven.<ref>{{Cite book|last=Grossnick|first=Roy|url=https://www.history.navy.mil/content/dam/nhhc/research/histories/naval-aviation/pdf/app16.pdf|title=United States Naval Aviation 1910-1995|publisher=Naval Historical Center|year=1997|isbn=0-945274-34-3|location=Naval History and Heritage Command, Washington, D.C.|pages=625}}</ref><ref>{{Cite web|url=https://www.collinsdictionary.com/dictionary/french-english/voler|title=English Translation of "voler" {{!}} Collins French-English Dictionary|website=www.collinsdictionary.com|language=en|access-date=2019-02-07}}</ref> The V has long been used by the U.S. Navy for heavier-than-air craft and possibly comes from the French [[volplane]].<ref>''United States Naval Aviation 1910–1995.'' Appendix 16: ''US Navy and Marine Corps Squadron Designations and Abbreviations.''</ref><ref>[https://www.dailypress.com/news/dp-xpm-20050417-2005-04-17-0504170205-story.html Military naming conventions: The ABCs of US ships], Daily Press</ref> Aircraft carriers are designated in two sequences: the first sequence runs from CV-1 USS ''[[USS Langley (CV-1)|Langley]]'' to the very latest ships, and the second sequence, "CVE" for escort carriers, ran from CVE-1 [[USS Long Island (CVE-1)|''Long Island'']] to CVE-127 [[USS Okinawa (CVE-127)|''Okinawa'']] before being discontinued.
* AV: Heavier-than-air aircraft tender, later [[List of seaplane carriers by country#United States AVs|Seaplane tender]] (retired)
* AVD: [[List of seaplane carriers by country#United States AVDs|Seaplane tender destroyer]] (retired)<ref>{{Cite web|date=2021-06-12|title=Flush-deck destroyers converted as seaplane tenders (AVD)|url=https://destroyerhistory.org/flushdeck/avd/|access-date=2021-10-11|archive-url=https://web.archive.org/web/20210612121543/https://destroyerhistory.org/flushdeck/avd/|archive-date=12 June 2021}}</ref>
* AVP: [[List of seaplane carriers by country#United States AVPs|Seaplane tender, Small]] (retired)
* AZ: Lighter-than-air aircraft tender (retired) (1920–1923)<ref name=Wright group=A>See {{USS|Wright|AZ-1}}.</ref>
* AVG: General-purpose aircraft tender (repurposed [[escort carrier]]) (1941–42)
* AVT (i) Auxiliary aircraft transport (retired)
* AVT (ii) Auxiliary training carrier (retired)
* ACV: Auxiliary aircraft carrier (escort carrier, replaced by CVE) (1942)
* CV: [[Fleet aircraft carrier]] (1921–1975), multi-purpose [[aircraft carrier]] (1975–present)
* CVA: Aircraft carrier, attack (category merged into CV, 30 June 1975)
* CV(N): Aircraft carrier, night (deck equipped with lighting and pilots trained for nighttime fights) (1944) (retired)
* CVAN: Aircraft carrier, attack, nuclear-powered (category merged into CVN, 30 June 1975)
* CVB: Aircraft carrier, large (original USS ''Midway'' class, category merged into CVA, 1952)
* CVE: [[List of United States Navy escort aircraft carriers|Aircraft carrier, escort]] (retired) (1943–retirement of type)
* CVHA: Aircraft carrier, helicopter assault (retired in favor of several LH-series [[amphibious assault ship]] hull codes)
* CVHE: Aircraft carrier, helicopter, escort (retired)
* CVL: [[Light aircraft carrier]] or aircraft carrier, small (retired)<ref>[https://www.history.navy.mil/content/dam/nhhc/research/histories/naval-aviation/Naval%20Aviation%20News/1940/pdf/1aug43.pdf Bureau of Aeronautics, Navy Department."New Carrier Designations". ''BuAER News'' (title later changed to ''Naval Aviation News''). Washington, D.C. No. 198 (1 Aug 1943) p. 9.]</ref><ref>[http://babel.hathitrust.org/cgi/pt?id=mdp.39015031962056;view=1up;seq=3 United States. Office of Naval History. ''Glossary of U.S. Naval Abbreviations''. 3d ed. Washington: U.S. Govt. Print. Off., 1947. p. 20.]</ref><ref>United States. Office of Naval Records and History. ''Glossary of US Naval Abbreviations''. 5th ed. Washington: U.S. Govt. Print. Off., 1949. [https://www.history.navy.mil/research/library/online-reading-room/title-list-alphabetically/u/us-navy-abbreviations-of-ww2.html Naval History and Heritage Command]. accessed 6 May 2017.</ref>
* CVN: Aircraft carrier, nuclear-powered
* CVS: [[Antisubmarine aircraft carrier]] (retired)
* CVT: Aircraft carrier, training (changed to AVT (auxiliary))
* CVU: Aircraft carrier, utility (retired)
* CVG: Aircraft carrier, guided missile (retired)
* CF: [[Flight deck cruiser]] (1930s, retired unused)
* CVV:<ref>{{Cite web |url=http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=AD0757047 |title=The Vari-Purpose Carrier |access-date=4 August 2011 |archive-url=https://web.archive.org/web/20160304053703/http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=AD0757047 |archive-date=4 March 2016 |url-status=dead }}</ref> [[Aircraft Carrier (Medium)|Aircraft carrier, vari-purpose, medium]] (retired unused)

==== Surface combatant type ====
Surface combatants are ships which are designed primarily to engage enemy forces on the high seas. The primary surface combatants are battleships, cruisers and destroyers. Battleships are very heavily armed and armored; cruisers moderately so; destroyers and smaller warships, less so. Before 1920, ships were called "<type> no. X", with the type fully pronounced. The types were commonly abbreviated in ship lists to "B-X", "C-X", "D-X" et cetera—for example, before 1920, {{USS|Minnesota|BB-22}} would have been called "USS ''Minnesota'', Battleship number&nbsp;22" orally and "USS ''Minnesota'', B-22" in writing. After 1920, the ship's name would have been both written and pronounced "USS ''Minnesota'' (BB-22)". In generally decreasing size, the types are:
* ACR: [[List of cruisers of the United States Navy#Armored cruisers (ACR)|Armored cruiser]] (pre-1920)
* AFSB: [[Afloat forward staging base]] (also AFSB(I) for "interim", changed to MLP ([[Mobile Landing Platform]], then ESD and ESB)
* B: Battleship (pre-1920)
* BB: [[List of battleships of the United States Navy|Battleship]]
* BBG: Battleship, guided missile or [[arsenal ship]] (never used operationally)<ref group=A>See {{USS|Kentucky|BB-66}}.</ref>
* BM: [[List of monitors of the United States Navy#"New Navy" monitors|Monitor]] (1920–retirement)
* C: [[List of cruisers of the United States Navy#Protected and Peace cruisers (C, PG)|Cruiser]] (pre-1920 protected cruisers and peace cruisers)
* CA: (first series) Cruiser, armored (retired, comprised all surviving pre-1920 armored and protected cruisers)
* CA: (second series) [[List of cruisers of the United States Navy#Heavy and light cruisers (CA, CL)|Heavy cruiser]], category later renamed gun cruiser (retired)
* CAG: [[List of cruisers of the United States Navy#Guided missile cruisers (CAG, CLG, CG)|Cruiser, heavy, guided missile]] (retired)
* CB:  [[List of cruisers of the United States Navy#Large cruisers (CB)|Large cruiser]] (retired)<ref group=A>See {{sclass|Alaska|cruiser|2}}.</ref>
* CBC: Large command cruiser (never used operationally)<ref group=A>See {{USS|Hawaii|CB-3}}.</ref>
* CC: (first usage) [[List of cruisers of the United States Navy#Battlecruisers (CC)|Battlecruiser]] (never used operationally)<ref group=A>See {{sclass|Lexington|battlecruiser|2}}.</ref>
* CC: (second usage) [[List of cruisers of the United States Navy#Command cruisers (CLC, CC)|Command cruiser]] (retired)
* CLC: Command cruiser, light (retired)<ref name=Northampton group=A>See {{USS|Northampton|CLC-1}}.</ref>
* CG: [[List of cruisers of the United States Navy#Guided missile cruisers (CAG, CLG, CG)|Cruiser, guided missile]]
* CGN: [[List of cruisers of the United States Navy#Guided missile cruisers (CAG, CLG, CG)|Cruiser, guided missile, nuclear-powered]]: {{USS|Long Beach|CGN-9}} and {{USS|Bainbridge|CGN-25}}
* CL: [[List of cruisers of the United States Navy#Heavy and light cruisers (CA, CL)|Cruiser, light]] (retired)
* CLAA: [[List of cruisers of the United States Navy#Antiaircraft cruisers (CLAA)|Cruiser, light, anti-aircraft]] (retired)
* CLD: [[CL-154-class cruiser#The CLD|Cruiser-destroyer, light]] (never used operationally)
* CLG: [[List of cruisers of the United States Navy#Guided missile cruisers (CAG, CLG, CG)|Cruiser, light, guided missile]] (retired)
* CLGN: Cruiser, light, guided missile, nuclear-powered (never used operationally)
* CLK: [[List of cruisers of the United States Navy#Hunter-Killer cruisers (CLK)|Cruiser, hunter–killer]] (never used operationally)<ref name=Norfolk group=A>see {{USS|Norfolk|DL-1}}.</ref>
* CM: [[List of cruisers of the United States Navy#Cruiser minelayers (CM)|Cruiser–minelayer]] (retired)
* CS: [[List of cruisers of the United States Navy#Scout cruisers (CS)|Scout cruiser]] (retired)
* CSGN: [[Strike cruiser|Cruiser, strike]], guided missile, nuclear-powered (never used operationally)
* D: Destroyer (pre-1920)
* DD: [[Destroyer]]
* DDC: Corvette (briefly proposed in the mid-1950s)<ref>{{cite book |title=U.S. Destroyers: An Illustrated Design History |edition=Revised  |last=Friedman |first=Norman |author-link=Norman Friedman |year=2003 |publisher=U.S. Naval Institute Press |location=Annapolis, MD |isbn=978-1-55750-442-5 |pages=266–267 |url=https://books.google.com/books?id=Tzp58htKLkEC&pg=PA266 |quote=...a gutted {{sclass|Benson|destroyer}}. This "corvette" (DDC) "can be readily obtained..."}}</ref>
* DDE: [[Escort destroyer]], a destroyer (DD) converted for [[antisubmarine warfare]] – category abolished 1962. (''not to be confused with destroyer escort DE'')
* DDG: [[Guided missile destroyer|Destroyer, guided missile]]
* DDK: Hunter–killer destroyer (category merged into DDE, 4 March 1950)
* DDR: [[Radar picket#US Navy World War II radar pickets|Destroyer, radar picket]] (retired)
* DE: [[Destroyer escort]] (World War II, later became [[Ocean escort]])
* DE: [[Ocean escort]] (abolished 30 June 1975)
* DEG: Guided missile ocean escort (abolished 30 June 1975)
* DER: Destroyer escort, radar picket (abolished 30 June 1975) There were two distinct breeds of DER, the DEs [[Radar picket#US Navy World War II radar pickets|which were converted to DERs during World War II]] and [[Radar picket#Destroyer Escort conversions|the more numerous postwar DER conversions]].
* DL: Destroyer leader (later frigate) (retired)
* DLG: Destroyer leader, guided missile (later frigate) (abolished 30 June 1975)
* DLGN: Destroyer leader, guided missile, nuclear-propulsion (later frigate) (abolished 30 June 1975) The DL category was established in 1951 with the abolition of the CLK category. CLK 1 became DL 1 and DD 927–930 became DL 2–5. By the mid-1950s the term destroyer leader had been dropped in favor of frigate. Most DLGs and DLGNs were reclassified as CGs and CGNs, 30 June 1975. However, DLG 6–15 became DDG 37–46. The old DLs were already gone by that time. Only applied to {{USS|Bainbridge|DLGN-25}}.
* DM: Destroyer, minelayer (retired)
* DMS: Destroyer, minesweeper (retired)
* FF: [[Frigate]]
* PF: Patrol frigate (retired)
* FFG: Frigate, guided missile
* FFH: Frigate with assigned helicopter<ref>Derdall and DiGiulian, (section: ''Torpedo Boats, Destroyers, Escorts and Frigates'')</ref>
* FFL: Frigate, light
* FFR: Frigate, radar picket (retired)
* FFT: Frigate (reserve training) (retired) The FF, FFG, and FFR designations were established 30 June 1975 as new type symbols for ex-DEs, DEGs, and DERs. The first new-built ships to carry the FF/FFG designation were the {{sclass|Oliver Hazard Perry|frigate}}s.
* PG: Patrol gunboat (retired)
* PCH: [[USS High Point|Patrol craft, hydrofoil]] (retired)
* PHM: [[Pegasus-class hydrofoil|Patrol, hydrofoil, missile]] (retired)
* K: [[Corvette]] (retired)
* LCS: [[Littoral combat ship]] In January 2015, the Navy announced that the up-gunned LCS will be reclassified as a frigate, since the requirements of the [[Littoral Combat Ship#Small surface combatant (SSC)|SSC Task Force]] was to upgrade the ships with frigate-like capabilities. The Navy is hoping to start retrofitting technological upgrades onto existing and under construction LCSs before 2019.<ref>[http://www.military.com/daily-news/2015/03/04/navy-plans-to-expand-speed-up-lcs-modifications.html?ESRC=todayinmil.sm Navy Plans to Expand, Speed-Up LCS Modifications] – Military.com, 4 March 2015</ref>
* LSES: Large Surface Effect Ship
* M: [[List of monitors of the United States Navy|Monitor]] (1880s–1920)
* SES: [[Surface effect ship|Surface Effect Ship]]
* TB: [[List of torpedo boats of the United States Navy|Torpedo boat]]

==== Submarine type ====
Submarines are all self-propelled submersible types (usually started with SS) regardless of whether employed as combatant, auxiliary, or research and development vehicles which have at least a residual combat capability. While some classes, including all diesel-electric submarines, are retired from USN service, non-U.S. navies continue to employ SS, SSA, SSAN, SSB, SSC, SSG, SSM, and SST types.<ref>Russia still employs several SSA and SSAN class submarines like the Delta Stretch as well as one SST, China has older SSB and SSG types such as the Golf and Mod Romeo classes, and North Korea has built many SSCs and SSMs. See 2007–2008 ''Jane{{'}}s Fighting Ships''.</ref> With the advent of new [[Air Independent Propulsion]]/Power (AIP) systems, both SSI and SSP are used to distinguish the types within the USN, but SSP has been declared the preferred term. SSK, retired by the USN, continues to be used colloquially and interchangeably with SS for diesel-electric attack/patrol submarines within the USN, and, more formally, by the Royal Navy and British firms such as [[Jane's Information Group]].
* SC: Cruiser Submarine (retired)
* SF: Fleet [[Submarine]] (retired)
* SM: Submarine Minelayer (retired)
* SS: Submarine, [[Attack Submarine]]<ref>[http://www.nvr.navy.mil/CLASS.HTM U.S. Navy Ship And Service Craft Classifications<!-- Bot generated title -->] {{webarchive|url=https://web.archive.org/web/20041016023831/http://www.nvr.navy.mil/class.htm |date=16 October 2004 }}</ref>
* SSA: Submarine Auxiliary, Auxiliary/Cargo Submarine
* SSAN: Submarine Auxiliary Nuclear, Auxiliary/Cargo Submarine, Nuclear-powered
* SSB: Submarine Ballistic, [[Ballistic missile submarine|Ballistic Missile Submarine]]
* SSBN: Submarine Ballistic Nuclear, [[Ballistic missile submarine|Ballistic Missile Submarine]], Nuclear-powered
* SSC: Coastal Submarine, over 150 tons
* SSG: [[Cruise missile submarine#U.S. Navy|Guided Missile Submarine]]
* SSGN: Guided Missile Submarine, Nuclear-powered<ref name=Halibut group=A>See {{USS|Halibut|SSGN-587}}.</ref>
* SSI: Attack Submarine (Diesel Air-Independent Propulsion)<ref>{{cite journal | last = Buff | first = Joe | author-link = Joe Buff
 |date=June 2007 | title = Subs in the Littoral: Diesels Just Blowing Smoke? | journal = Proceedings of the Naval Institute
 | volume = 133 | issue = 6 | pages = 40–43 | issn = 0041-798X | url = http://www.usni.org/ | access-date = 2007-06-13
 | quote = Diesel AIP boats are known as SSIs, differentiating them from purely diesel-electric-powered hunter-killer subs, or SSKs. }}</ref>
* [[SSK (hull classification symbol)|SSK]]: [[Hunter-killer submarine|Hunter-Killer]]/ASW Submarine (retired)<ref>[http://www.nvr.navy.mil/oldclass.htm Inactive Classification Symbols<!-- Bot generated title -->] {{webarchive|url=https://web.archive.org/web/20120118095120/http://www.nvr.navy.mil/oldclass.htm |date=18 January 2012 }}</ref>
* [[SSKN]]: Hunter-Killer/ASW Submarine, Nuclear-powered (retired)
* SSM: Midget Submarine, under 150 tons
* [[SSN (hull classification symbol)|SSN]]: [[Attack submarine|Attack Submarine]], Nuclear-powered
* SSNR: Special Attack Submarine<ref group="note">This odd entry is not recognized by the U.S. Naval Vessel Register, and appears only in MIL-STD-2525A: ''Common Warfighting Symbology'' (15 December 1996) and later editions (MIL-STD-2525B: ''Common Warfighting Symbology'' (30 January 1999) and MIL-STD-2525C: ''Common Warfighting Symbology'' (17 November 2008)). It seems to refer to some kind of nuclear-powered submarine used by Special Operations Forces.</ref>
* SSO: Submarine Oiler (retired)<ref name=Guavina group=A>See {{USS|Guavina|SSO-362}}.</ref>
* SSP: Attack Submarine (Diesel Air-Independent Power) (alternate use), formerly Submarine Transport
* SSQ: Auxiliary Submarine, Communications (retired)
* SSQN: Auxiliary Submarine, Communications, Nuclear-powered (retired)<ref>[http://www.dia.mil/publicaffairs/Foia/abbrev_acron.pdf 28034_cov.fh<!-- Bot generated title -->] {{webarchive|url=https://web.archive.org/web/20070927024419/http://www.dia.mil/publicaffairs/Foia/abbrev_acron.pdf |date=27 September 2007 }}</ref>
* SSR: [[Radar picket#Converted and purpose-built submarines|Radar Picket Submarine]] (retired)
* SSRN: Radar Picket Submarine, Nuclear-powered (retired)<ref name=Triton group=A>See {{USS|Triton|SSRN-586}}.</ref>
* SST: Training Submarine
* SSV: [[Submarine aircraft carrier|Submarine Aircraft Carrier]] (never used)
{|
|style="width: 50%;"|
* AGSS: Auxiliary Submarine
* AOSS: Submarine Oiler (retired)
* ASSP: Transport Submarine (retired)
* APSS: Transport Submarine (retired)
* LPSS: Amphibious Transport Submarine (retired)
* SSLP: Transport Submarine (retired)
|SSP, ASSP, APSS, and LPSS were all the same type, redesignated over the years.
|}
* X: [[Midget submarine]]<ref name=X-1 group=A>See [[X-1 submarine]].</ref>
* IXSS: Unclassified Miscellaneous Submarine
* MTS: Moored Training Ship ([[Naval Nuclear Power School]] Training Platform; reconditioned SSBNs and SSNs)

==== Patrol combatant type ====
Patrol combatants are ships whose mission may extend beyond coastal duties and whose characteristics include adequate endurance and seakeeping, providing a capability for operations exceeding 48&nbsp;hours on the high seas without support. This notably included [[Brown Water Navy]]/Riverine Forces during the Vietnam War. Few of these ships are in service today.
* PBR: [[Patrol Boat, River]], Brown Water Navy (Pibber or PBR-Vietnam)
* PC: Coastal Patrol, originally [[Submarine chaser|Sub Chaser]]
* PCF: [[Patrol Craft, Fast]]; Swift Boat, Brown Water Navy (Vietnam)
* PE: [[Eagle-class patrol craft|Eagle Boat]] of [[World War I]]
* PF: World War II Frigate, based on British {{sclass2|River|frigate|4}}.
** PFG: Original designation of {{USS|Oliver Hazard Perry|FFG-7}}
* PG: WWII-era [[Gunboat]]s, later Patrol combatant, with ability to operate in rivers; what is generally known as [[River gunboat]]s
* PGH: Patrol Combatant, Hydrofoil ({{USS|High Point}})
* PHM: Patrol, [[Hydrofoil]] Missile ({{sclass|Pegasus|hydrofoil}})
* PR: Patrol, River, such as the {{USS|Panay|PR-5}}
* PT: [[PT Boat|Patrol Torpedo Boat]], the U.S. take on the [[Motor Torpedo Boat]] (World War II)
* PTF:[[Patrol Torpedo Fast]], Brown Water Navy (Vietnam)
* PTG/PTGB: Patrol Torpedo Gunboat
* [[List of monitors of the United States Navy|Monitor]]: Heavily gunned riverine boat, Brown Water Navy (Vietnam and prior). Named for {{USS|Monitor}}
* ASPB: [[Assault Support Patrol Boat]], "Alpha Boat", Brown Water Navy; also used as riverine minesweeper (Vietnam)
* [[PACV]]: [[Patrol Air Cushion Vehicle]], [[hovercraft]] that was part of the Brown Water Navy (Vietnam)
* SP: [[Section Patrol]], used indiscriminately for [[patrol vessel]]s, [[Minelayer|mine warfare vessels]], and some other types (World War I; retired 1920)

==== Amphibious warfare type ====
Amphibious warfare vessels include all ships having an organic capability for amphibious warfare and which have characteristics enabling long duration operations on the high seas. There are two classifications of craft: [[amphibious warfare ship]]s, which are built to cross oceans, and [[landing craft]], which are designed to take troops from ship to shore in an invasion.

The U.S. Navy hull classification symbol for a ship with a [[Well dock|well deck]] depends on its [[Aviation-capable naval vessel|facilities for aircraft]]:
* An [[Dock landing ship|LSD]] has a [[helicopter deck]], which was removable in the older ships.
* An [[Amphibious transport dock|LPD]] has a hangar in addition to the helicopter deck.
* An [[Landing Helicopter Dock|LHD]] or [[Landing Helicopter Assault|LHA]] has a full-length flight deck.<ref>{{cite web |url=http://www.globalsecurity.org/military/world/amphibious-dock.htm|title=World Wide Landing Ship Dock/Landing Platform Dock|access-date=2012-05-17}}</ref>

Ships
* AKA: [[List of United States Navy amphibious warfare ships#Attack Cargo Ship (AKA)|Attack Cargo Ship]] (To LKA, 1969)
* APA: [[List of United States Navy amphibious warfare ships#Attack Transport (APA)|Attack Transport]] (To LPA, 1969)
* APD: [[List of United States Navy amphibious warfare ships#High-speed Transport (APD)|High speed transport]] (Converted Destroyer or Destroyer Escort) (To LPR, 1969)
* APM: [[List of United States Navy amphibious warfare ships#Mechanized Artillery Transports (APM)|Mechanized Artillery Transports]] (To LSD)
* AGC: [[List of United States Navy amphibious warfare ships#Amphibious Force Flagship (AGC)|Amphibious Force Flagship]] (To LCC, 1969)
* LCC: (second usage) [[List of United States Navy amphibious warfare ships#Amphibious Command Ship (LCC)|Amphibious Command Ship]]
* LHA: General-Purpose Amphibious Assault Ship, also known as [[List of United States Navy amphibious warfare ships#Amphibious Assault Ship (General Purpose) (LHA)|Landing ship, Helicopter, Assault]]
* LHD: Multi-Purpose Amphibious Assault Ship, also known as [[List of United States Navy amphibious warfare ships#Amphibious Assault Ship (Multi-Purpose) (LHD)|Landing ship, Helicopter, Dock]]
* LKA: [[List of United States Navy amphibious warfare ships#Amphibious Cargo Ship (LKA)|Amphibious Cargo Ship]] (out of commission)
* LPA: [[List of United States Navy amphibious warfare ships#Amphibious Transport (LPA)|Amphibious Transport]]
* LPD: [[List of United States Navy amphibious warfare ships#Landing Platform Dock (LPD)|Amphibious transport dock]], also known as Landing ship, Personnel, Dock
* LPH: [[List of United States Navy amphibious warfare ships#Landing Platform Helicopter (LPH)|Landing ship, Personnel, Helicopter]]<ref name=Friedman2002>{{cite book|last=Friedman |first=Norman |title=U.S. Amphibious Ships and Craft: An Illustrated Design History |publisher=Naval Institute Press |year=2002 |series=Illustrated Design Histories |page=656 |isbn=1-55750-250-1 |url=https://books.google.com/books?id=oWX-x0b4pw4C&pg=PA218 }}</ref>
* LPR: [[List of United States Navy amphibious warfare ships#Amphibious Transport, Small (LPR)|High speed transport]]
* LSD: [[List of United States Navy amphibious warfare ships#Landing Ship Dock (LSD)|Landing Ship, Dock]]
* LSH: [[Landing Ship Heavy|Landing Ship, Heavy]]
* LSIL: [[Landing Ship, Infantry]] (Large) (formerly LCIL)
* LSL: [[Landing Ship Logistics|Landing Ship, Logistics]]
* LSM: [[List of United States Navy Landing Ship Medium (LSMs)|Landing Ship, Medium]]
** LSM(R): Landing Ship, Medium (Rocket)
* LSSL: [[Landing Craft Support|Landing Ship, Support (Large)]] (formerly LCSL)
* LST: [[List of United States Navy LSTs|Landing Ship, Tank]]
** LST(H): [[Landing Ship, Tank (Hospital)]]
* LSV: [[List of United States Navy amphibious warfare ships#Vehicle Landing Ship (LSV)|Landing Ship, Vehicle]]

Landing Craft
* LCA: [[Landing Craft Assault|Landing Craft, Assault]]
* LCAC: [[Landing Craft Air Cushion]]
* LCC: (first usage) Landing Craft, Control
* LCFF: (Flotilla Flagship)
* LCH: Landing Craft, Heavy
* LCI: [[Landing Craft Infantry|Landing Craft, Infantry]], World War II-era classification further modified by
** (G) – Gunboat
** (L) – Large
** (M) – Mortar
** (R) – [[Landing Craft Infantry#LCI(R) – Rocket|Rocket]]
* LCL: [[Landing Ship Logistics|Landing Craft, Logistics]] (UK)
* LCM: [[Landing Craft Mechanized|Landing Craft, Mechanized]]
* LCP: Landing Craft, Personnel
* LCP(L): [[LCPL|Landing Craft, Personnel, Large]]
* LCP(R): [[LCPR|Landing Craft, Personnel, Ramped]]
* LCPA: Landing Craft, Personnel, Air-Cushioned
* LCS(L): [[Landing Craft Support|Landing Craft, Support (Large)]] changed to '''LSSL''' in 1949
* LCT: [[Landing craft tank|Landing Craft, Tank]] (World War II era)
* LCU: [[Landing Craft Utility|Landing Craft, Utility]]
* LCVP: [[LCVP (United States)|Landing Craft, Vehicle and Personnel]]
* LSH: [[Landing Ship Heavy]] (Royal Australian Navy)

====Expeditionary support====
Operated by Military Sealift Command, have ship prefix "USNS", hull code begins with "T-".
* EMS: [[List of United States Navy amphibious warfare ships#Expeditionary Medical Ship (EMS)|Expeditionary Medical Ship]], an EPF modified into a hospital ship<ref name=USNI_20230515>{{cite news|title=SECNAV Del Toro Names New Class of Medical Ships After Bethesda Medical Center |date=May 2023 |first=Heather |last=Mongilio |url=https://news.usni.org/2023/05/15/secnav-del-toro-names-new-class-of-medical-ships-after-bethesda-medical-center |newspaper=USNI News |publisher=United States Naval Institute }}</ref>
* EPF: [[List of United States Navy amphibious warfare ships#Expeditionary Fast Transport (EPF)|Expeditionary fast transport]]
* ESB: [[Expeditionary Mobile Base]] (a variant of ESD, formerly  Afloat Forward Staging Base (AFSB))
* ESD: [[List of United States Navy amphibious warfare ships#Expeditionary Transfer Dock (ESD)|Expeditionary Transfer Dock]]
* HST: [[HST-2|High-Speed Transport]] (similar to JHSV, not to be confused with WWII-era [[High-speed transport]] (APD))
* HSV: High-Speed Vessel
* JHSV: Joint High-Speed Vessel (changed to EPF)
* MLP: Mobile Landing Platform (changed to ESD)

==== Mine warfare type ====
Mine warfare ships are those ships whose primary function is [[Minelaying|mine warfare]] on the high seas.
* ADG: [[List of mine warfare vessels of the United States Navy#Degaussing Ships (ADG)|Degaussing ship]]
* AM: [[Minesweeper]]
* AMb: Harbor minesweeper
* AMc: Coastal minesweeper
* AMCU: Underwater mine locater
* AMS: Motor minesweeper
* CM: Cruiser (i.e., large) minelayer
* CMc: Coastal minelayer
* DM: High-speed minelayer (converted destroyer)
* DMS: High-speed minesweeper (converted-destroyer)
* PCS: Submarine chasers (wooden) fitted for minesweeping<ref>{{cite web|url=http://militarypower.wikidot.com/hull-classification-symbol|title=Hull Classification Symbol|publisher=militarypower.wikidot.com|access-date=17 January 2018}}</ref>
* YDG: District degaussing vessel

In 1955 all mine warfare vessels except for degaussing vessels had their hull codes changed to begin with "M".
* MCM: [[Mine countermeasures ship]]
* MCS: [[List of mine warfare vessels of the United States Navy#Mine Countermeasures Support Ships (MCS)|Mine countermeasures support ship]]
* MH(C)(I)(O)(S): [[Minehunter]], (coastal) (inshore) (ocean) (hunter and sweeper, general)
* MLC: Coastal minelayer
* MSC: [[Coastal minesweeper|Minesweeper, coastal]]
* MSF: Minesweeper, steel hulled
* MSO: [[Ocean minesweeper|Minesweeper, ocean]]

==== Coastal defense type ====
Coastal defense ships are those whose primary function is coastal patrol and interdiction.
* FS: [[Corvette]]
* PB: [[Patrol boat]]
* PBR: [[Patrol boat]], river
* PC: [[Patrol craft|Patrol]], coastal
* PCE: Patrol craft, escort
* PCF: Patrol craft, fast, (swift boat)
* PCS: Patrol craft, sweeper (modified-motor minesweepers meant for anti-submarine warfare)
* PF: [[Frigate]], in a role similar to World War II Commonwealth [[corvette]]
* PG: Patrol [[Gunboat#Early Modern era|gunboat]]
* PGM: Motor gunboat (To PG, 1967)
* PR: Patrol, [[River gunboat|river]]
* SP: [[Section patrol]]

=== Auxiliaries ===
An auxiliary ship is designed to operate in any number of roles supporting combatant ships and other naval operations.

==== Combat logistics type ====
Ships which have the capability to provide [[underway replenishment]] (UNREP) to fleet units.
* AE: [[List of auxiliaries of the United States Navy#Ammunition Ships (AE)|Ammunition ship]]
* AF: [[Reefer ship]] / Stores ship (retired)
* AFS: [[List of auxiliaries of the United States Navy#Combat Stores Ships (AFS, T-AFS)|Combat stores ship]]
* AK: [[List of auxiliaries of the United States Navy#Dry Cargo Ships (AK, T-AK)|Dry cargo ship]]
* AKE: [[List of auxiliaries of the United States Navy#Advanced Auxiliary Dry Cargo Ships (T-AKE)|Advanced dry cargo ship]]
* AKS: [[List of auxiliaries of the United States Navy#General Stores Issue Ships (AKS)|General stores ship]]
* AO: [[List of United States Navy oilers#Fleet Oilers (AO)|Fleet Oiler]]
* AOE: [[List of United States Navy oilers#Fast Combat Support Ships (AOE)|Fast combat support ship]]
* AOL: [[List of United States Navy oilers#Light Replenishment Oilers (T-AOL)|Light replenishment oiler]]<ref group=A>In 2020 the US Navy began to develop this new type of ship, construction of the first is planned for 2026</ref><ref name=USNI_20230428>{{cite news|title=Report to Congress on Navy Light Replenishment Oiler |date=April 2023 |url=https://news.usni.org/2023/04/28/report-to-congress-on-navy-light-replenishment-oiler |newspaper=USNI News |publisher=United States Naval Institute }}</ref>
* AOR: [[List of United States Navy oilers#Fleet Replenishment Oilers (AOR)|Replenishment oiler]]
* AVS: [[List of auxiliaries of the United States Navy#Aviation Stores Issue Ships (AVS)|Aviation Stores Issue Ship]] (retired)

==== Mobile logistics type ====
Mobile logistics ships have the capability to provide direct material support to other deployed units operating far from home ports.
* AC: [[List of auxiliaries of the United States Navy#Colliers (AC)|Collier]] (retired)
* AD: [[List of auxiliaries of the United States Navy#Destroyer Tenders (AD)|Destroyer tender]]
* AGP: [[List of auxiliaries of the United States Navy#Motor Torpedo Boat Tenders (AGP)|Patrol craft tender]]
* AR: [[List of auxiliaries of the United States Navy#Repair Ships (AR)|Repair ship]]
* ARB: [[List of auxiliaries of the United States Navy#Battle Damage Repair Ships (ARB)|Repair ship, battle damage]]
* ARC: [[List of auxiliaries of the United States Navy#Cable Repair Ships (ARC)|Repair ship, cable]]
* ARG: [[List of auxiliaries of the United States Navy#Internal Combustion Engine Repair Ships (ARG)|Repair ship, internal combustion engine]]
* ARH: Repair ship, heavy-hull<ref name=Jason group=A>See {{USS|Jason|ARH-1}}.</ref>
* ARL: [[List of auxiliaries of the United States Navy#Landing Craft Repair Ships (ARL)|Repair ship, landing craft]]
* ARV: Repair ship, aircraft
* ARVH: Repair ship, aircraft, helicopter
* AS: [[List of auxiliaries of the United States Navy#Submarine Tenders (AS)|Submarine tender]]
* AW: [[Distilling ship]] (retired)

==== Support ships ====
Support ships are not designed to participate in combat and are generally not armed. For ships with civilian crews (owned by and/or operated for [[Military Sealift Command]] and the [[United States Maritime Administration|Maritime Administration]]), the prefix T- is placed at the front of the hull classification.

Support ships are designed to operate in the open ocean in a variety of sea states to provide general support to either combatant forces or shore-based establishments. They include smaller auxiliaries which, by the nature of their duties, leave inshore waters.

* AB: Auxiliary Crane Ship (1920–41)<ref group=A>See [[USS Crane Ship No. 1]]</ref>
* ACS: [[List of auxiliaries of the United States Navy#Auxiliary Crane Ships (T-ACS)|Auxiliary Crane Ship]]
* AG: [[List of auxiliaries of the United States Navy#Miscellaneous Ships (AG, T-AG)|Miscellaneous Auxiliary]]
* AGB: [[List of auxiliaries of the United States Navy#Icebreakers (AGB)|Icebreaker]]
* AGDE: Testing Ocean Escort<ref group=A>See {{USS|Glover|AGDE-1}}</ref>
* AGDS: [[List of auxiliaries of the United States Navy#Deep Submergence Support Ship (T-AGDS)|Deep Submergence Support Ship]]
* AGEH: Hydrofoil, experimental<ref group=A>See {{USS|Plainview|AGEH-1}}</ref>
* AGER: (i): Miscellaneous Auxiliary, Electronic Reconnaissance
* AGER: (ii): [[List of auxiliaries of the United States Navy#Environmental Research Ships (AGER)|Environmental Research Ship]]
* AGF: [[List of auxiliaries of the United States Navy#Command Ships (AGF)|Miscellaneous Command Ship]]
* AGFF: Testing Frigate<ref group=A>See {{USS|Glover|AGFF-1}}</ref>
* AGHS: Patrol combatant support ship—ocean or inshore
* AGL: Auxiliary vessel, [[lighthouse tender]]
* AGM: [[List of auxiliaries of the United States Navy#Missile Range Instrumentation Ships (T-AGM)|Missile Range Instrumentation Ship]]
* AGMR: [[List of auxiliaries of the United States Navy#Major Communications Relay Ships (AGMR)|Major Communications Relay Ship]]
* AGOR: [[List of auxiliaries of the United States Navy#Oceanographic Research Ships (T-AGOR)|Oceanographic Research Ship]]
* AGOS: [[List of auxiliaries of the United States Navy#Ocean Surveillance Ships (T-AGOS)|Ocean Surveillance Ship]]
* AGR: [[List of auxiliaries of the United States Navy#Radar Picket Ships (AGR)|Radar picket ship]]
* AGS: [[List of auxiliaries of the United States Navy#Surveying Ships (AGS)|Surveying Ship]]
* AGSC: [[List of auxiliaries of the United States Navy#Coastal Survey Ships (AGSC)|Coastal Survey Ships]]
* AGSE: Submarine and Special Warfare Support
* AGTR: [[List of auxiliaries of the United States Navy#Technical Research Ships (AGTR)|Technical research ship]]
* AH: [[List of auxiliaries of the United States Navy#Hospital Ships (AH)|Hospital ship]]
* AKD: Cargo Ship, Dock<ref group=A>See {{USS|Point Barrow|AKD-1}}</ref>
* AKL: [[List of auxiliaries of the United States Navy#Small Cargo Ships (AKL)|Cargo Ship, Small]]
* AKN: [[List of auxiliaries of the United States Navy#Net Cargo Ships (AKN)|Cargo Ship, Net]]
* AKR: [[List of auxiliaries of the United States Navy#Vehicle Cargo Ships (T-AKR)|Cargo Ship, Vehicle]]
* AKV: [[List of auxiliaries of the United States Navy#Aircraft Transports (AKV, T-AKV)|Cargo Ship, Aircraft]]
* AN: [[List of auxiliaries of the United States Navy#Net Laying Ships (AN)|Net laying ship]]
* AOG: [[List of auxiliaries of the United States Navy#Gasoline Tankers (AOG, T-AOG)|Gasoline tanker]]
* AOT: [[List of United States Navy oilers#Transport Oilers (AOT)|Transport Oiler]]
* AP: [[List of auxiliaries of the United States Navy#Transports (AP, T-AP)|Transport]]
* APB: [[List of auxiliaries of the United States Navy#Self-Propelled Barracks Ships (APB)|Self-propelled Barracks Ship]]
* APC: [[List of auxiliaries of the United States Navy#Coastal Transports (APC)|Coastal Transport]]
* APc: [[List of auxiliaries of the United States Navy#Small Coastal Transports (APc)|Coastal Transport, Small]]
* APH: [[List of auxiliaries of the United States Navy#Evacuation Transports (APH)|Evacuation Transport]]
* APL: [[List of auxiliaries of the United States Navy#Barracks Craft (APL)|Barracks Craft]]
* ARS: [[List of auxiliaries of the United States Navy#Rescue and Salvage Ships (ARS)|Rescue and Salvage Ship]]
* ARSD: [[List of auxiliaries of the United States Navy#Salvage Lifting Vessels (ARSD)|Salvage Lifting Vessels]]
* ASR: [[List of auxiliaries of the United States Navy#Submarine Rescue Vessels (ASR)|Submarine Rescue Ship]]
* AT: [[List of auxiliaries of the United States Navy#Fleet Tugs (AT)|Fleet Tug]]
* ATA: [[List of auxiliaries of the United States Navy#Auxiliary Ocean Tugs (ATA, T-ATA)|Auxiliary Ocean Tug]]
* ATF: [[List of auxiliaries of the United States Navy#Fleet Ocean Tugs (ATF, T-ATF)|Fleet Ocean Tug]]
* ATLS: Drone Launch Ship
* ATO: [[List of auxiliaries of the United States Navy#Fleet Tugs, Old (ATO)|Fleet Tug, Old]]
* ATR: [[List of auxiliaries of the United States Navy#Rescue Tugs (ATR)|Rescue Tug]]
* ATS: [[List of auxiliaries of the United States Navy#Salvage and Rescue Ships (ATS)|Salvage and Rescue Ship]]
* AVB(i): Aviation Logistics Support Ship
* AVB(ii): Advance Aviation Base Ship
* AVM: Guided Missile Ship<ref group=A>See {{USS|Norton Sound|AVM-1}}</ref>
* AVT(i): Auxiliary Aircraft Transport
* AVT(ii): Auxiliary Aircraft Landing Training Ship
* EPCER: Experimental – Patrol Craft Escort – Rescue
* PCER: Patrol Craft Escort – Rescue<ref>{{cite web|url=http://www.navsource.net/archives/12/02848.htm|title=PCER-848|publisher=navsource|access-date=21 December 2017}}</ref>
* SBX: [[Sea-based X-band Radar]] – a mobile [[active electronically scanned array]] [[early-warning radar]] station.

==== Service type craft ====
Service craft are navy-subordinated craft (including non-self-propelled) designed to provide general support to either combatant forces or shore-based establishments. The suffix "N" refers to non-self-propelled variants.
* AFDB: [[Auxiliary floating drydock|Large Auxiliary]] Floating [[Dry Dock]]
* AFD/AFDL: [[Auxiliary floating drydock|Small Auxiliary Floating Dry Dock]]
* AFDM: [[Auxiliary floating drydock|Medium Auxiliary Floating Dry Dock]]
* ARD: [[Auxiliary floating drydock|Auxiliary Repair Dry Dock]]
* ARDM: [[Auxiliary floating drydock|Medium Auxiliary Repair Dry Dock]]  {{USS|Oak Ridge|ARDM-1}}
* JUB/JB: Jack Up Barge

==== Submersibles ====
* DSRV: [[Deep Submergence Rescue Vehicle]]
* DSV: [[Deep Submergence Vehicle]]
* NR: Submersible Research Vehicle<ref name=NR-1 group=A>See [[Deep Submergence Vessel NR-1]].</ref>

=== Yard and district craft ===
* YAG: Miscellaneous Auxiliary Service
* YC: [[Open Lighter]]
* YCF: [[Car Float]]
* YCV: Aircraft Transportation Lighter
* YD: Floating [[Crane (machine)|Crane]]
* YDT: Diving Tender
* YF: [[Covered Lighter]]
* YFB: [[Ferry Boat]] or Launch
* YFD: [[Auxiliary floating drydock|Yard Floating Dry Dock]]
* YFN: Covered Lighter (non-self propelled)
* YFNB: Large Covered Lighter (non-self propelled)
* YFND: Dry Dock Companion Craft (non-self propelled)
* YFNX: Lighter (Special purpose) (non-self propelled)
* YFP: [[Type B ship|Floating Power Barge]]
* YFR: [[Type B ship|Refrigerated Cover Lighter]]
* YFRN: [[Type B ship|Refrigerated Covered Lighter]] (non-self propelled)
* YFRT: [[Range Tender]] [[USNS Range Recoverer (T-AG-161)|USNS ''Range Recoverer'' (T-AG-161)]]
* YFU: Harbor Utility Craft
* YG: [[Type B ship|Garbage Lighter]]
* YGN: [[Type B ship|Garbage Lighter]] (non-self propelled)
* YH: [[Water ambulance|Ambulance boat]]/small medical support vessel
* YLC: Salvage Lift Craft
* YM: [[Dredge]]
* YMN: [[Dredge]] (non-self propelled)
* YNG: [[Net tender|Net Gate Craft]]
* YN: [[Net tender|Yard Net Tender]]
* YNT: [[Net tender|Net Tender]]
* YO: [[Type B ship|Fuel Oil]] [[Barge]]
* YOG: [[Type B ship|Gasoline Barge]]
* YOGN: [[Type B ship|Gasoline Barge]] (non-self propelled)
* YON: [[Type B ship|Fuel Oil Barge]] (non-self propelled)
* YOS: [[Type B ship|Oil Storage Barge]]
* YP: [[Yard patrol boat|Patrol Craft, Training]]
* YPD: Floating Pile Driver
* YR: Floating Workshop
* YRB: [[Type B ship|Repair and Berthing Barge]]
* YRBM: Repair, Berthing and Messing Barge
* YRDH: Floating Dry Dock Workshop (Hull)
* YRDM: Floating Dry Dock Workshop (Machine)
* YRR: [[Yard Repair Berthing and Messing|Radiological Repair Barge]] nuclear ships and submarines service
* YRST: [[Laysan Island-class salvage craft tender|Salvage Craft Tender]]
* YSD: [[YSD-11 Class Seaplane Wrecking Derrick|Seaplane Wrecking Derrick]] – Yard Seaplane Derrick
* YSR: Sludge Removal Barge
* YT:  [[Type V ship|Harbor Tug]] (craft later assigned YTB, YTL, or YTM classifications)
* YTB: [[Type V ship|Large]] [[Harbor tug]]
* YTL: [[Type V ship|Small Harbor Tug]]
* YTM: [[Type V ship|Medium Harbor Tug]]
* YTT: [[Torpedo trials craft]]
* YW: [[Type B ship|Water Barge]]
* YWN: [[Type B ship|Water Barge]] (non-self propelled)

=== Miscellaneous ships and craft ===
* ID or Id. No.: [[Section patrol craft#Identification numbers (ID)|Civilian ship taken into service for auxiliary duties]], used indiscriminately for large ocean-going ships of all kinds and coastal and yard craft (World War I; retired 1920)
* IX: [[List of unclassified miscellaneous vessels of the United States Navy|Unclassified Miscellaneous Unit]]
* "none": To honor her unique historical status, [[USS Constitution|USS ''Constitution'']], formerly IX 21, was reclassified to "none", effective 1 September 1975.

=== Airships ===
Although aircraft, pre-World War II rigid airships were commissioned (no different from surface warships and submarines), flew the U.S. ensign from their stern and carried a United States Ship (USS) designation.

Rigid airships:
* ZR: [[List of airships of the United States Navy#Fabric-clad rigid airships|Rigid airship]]
* ZRS: Rigid airship scout<ref name=Akron group=A>See [[Akron-class airship]].</ref>
* [[ZRCV]]: Rigid airship aircraft carrier, proposed, not built

Lighter-than-air aircraft (e.g., [[blimp]]s) continued to fly the U.S. ensign from their stern but were registered as aircraft:
{{main|List of United States Navy aircraft designations (pre-1962)#Pre-1954 airship systems|List of United States Navy aircraft designations (pre-1962)#Other airships}}

=== Temporary designations ===
United States Navy Designations (Temporary) are a form of U.S. Navy ship designation, intended for temporary identification use. Such designations usually occur during periods of sudden mobilization, such as that which occurred prior to, and during, [[World War II]] or the [[Korean War]], when it was determined that a sudden temporary need arose for a ship for which there was no official Navy designation.

During [[World War II]], for example, a number of commercial vessels were requisitioned, or acquired, by the U.S. Navy to meet the sudden requirements of war. A [[yacht]] acquired by the U.S. Navy during the start of World War II might seem desirable to the Navy whose use for the vessel might not be fully developed or explored at the time of acquisition.

On the other hand, a U.S. Navy vessel, such as the yacht in the example above, already in commission or service, might be desired, or found useful, for another need or purpose for which there is no official designation.
* IX: Unclassified Miscellaneous Auxiliary Ship, for example, yacht ''Chanco'' acquired by the U.S. Navy on 1 October 1940. It was classified as a [[minesweeper]] {{USS|Kestrel|AMc-5|1}}, but instead, mainly used as a [[patrol craft]] along the [[New England]] coast. When another assignment came, and it could not be determined how to classify the vessel, it was redesignated IX-175 on 10 July 1944.
* IXSS: Unclassified Miscellaneous Submarines, such as the {{USS|Cod|IXSS-224}}, the {{USS|Angler|IXSS-240}} and the {{USS|Croaker|IXSS-246}}.
* YAG: Miscellaneous Auxiliary Service Craft, such as the {{USS|George Eastman|YAG-39}}, {{USS|Butternut|YAG-60}} and {{USS|Christiana|YAG-32}} which, curiously, was earlier known as {{USS|Christiana|IX-80|1}}.

Numerous other U.S. Navy vessels were launched with a temporary, or nominal, designation, such as YMS or PC, since it could not be determined, at the time of construction, what they should be used for. Many of these were vessels in the 150 to 200 feet length class with powerful engines, whose function could be that of a [[minesweeper]], [[patrol craft]], [[submarine chaser]], [[seaplane tender]], [[tugboat]], or other. Once their destiny, or capability, was found or determined, such vessels were reclassified with their actual designation.

== United States Coast Guard vessels ==
Prior to 1965, U.S. Coast Guard cutters used the same designation as naval ships but preceded by a "W" to indicate Coast Guard commission. The U.S. Coast Guard considers any ship over 65 feet in length with a permanently assigned crew, a cutter.<ref>{{cite web |title=United States Coast Guard |url=https://www.uscg.mil/datasheet/dataindx.htm |access-date=27 April 2020 |archive-url=https://web.archive.org/web/20060101111600/http://www.uscg.mil/datasheet/index.shtm |archive-date=1 January 2006 |language=en |date=1 January 2006 |url-status=dead}}</ref>

=== Current USCG cutter classes and types ===
{{#section-h:United_States_Coast_Guard_Cutter|Current USCG cutter classes and types}}

=== Historic USCG cutter classes and types ===
{{#section-h:United_States_Coast_Guard_Cutter|Historic USCG cutter classes and types}}

=== USCG classification symbols definitions ===
* CG: all Coast Guard ships in the 1920s (retired)
* WAGB: Coast Guard {{sclass2|Polar|icebreaker}}
* WAGL: Auxiliary vessel, lighthouse tender (retired 1960's)
* WAVP: seagoing Coast Guard seaplane tenders (retired 1960s)
* WDE: seagoing Coast Guard destroyer escorts (retired 1960s)
* WHEC: Coast Guard high endurance cutters
* WIX: Coast Guard barque {{USCGC|Eagle|WIX-327|2}}
* WLB: Coast Guard [[buoy tender]]s
* WLBB: Coast Guard seagoing buoy tenders/ice breaker
* WLI: Coast Guard inland buoy tenders
* WLIC: Coast Guard inland construction tenders
* WLM: Coast Guard coastal buoy tenders
* WLR: Coast Guard river buoy tenders
* WMEC: Coast Guard medium endurance cutters
* WMSA: Arctic Security Cutter
* WMSL: Coast Guard maritime security cutter, large (referred to as national security cutters)
* WMSP: Polar Security Cutter
* WPB: Coast Guard patrol boats
* WPC: Coast Guard patrol craft—later reclassed under WHEC, symbol reused for Coast Guard patrol cutter (referred to as [[Sentinel-class cutter|fast response cutters]])
* WPG: seagoing Coast Guard gunboats (retired 1960s)
* WTGB: [[Bay-class tugboat|Coast Guard tug boat]] (140' icebreakers)
* WYTL: [[USCG 65' Small harbor tug|Small harbor tug]]

=== USCG classification symbols for small craft and boats ===
* MLB: [[Motor Life Boat]] (52', 47', and 44' variants)
* UTB: Utility Boat 
* DPB: [[USCG Deployable Pursuit Boat|Deployable Pursuit Boat]]
* ANB: [[Aids to Navigation Boat]]s
* TPSB: [[Transportable Port Security Boat]]
* RHIB: [[Rigid inflatable boat|Rigid Hull Inflatable Boats]]
* SRB: Surf Rescue Boat (30')

== National Oceanic and Atmospheric Administration hull codes ==
* R: Research ships, including oceanographic and fisheries research ships
* S: Survey ships, including hydrographic survey ships

The letter is paired with a three-digit number. The first digit of the number is determined by the ship{{'}}s "power tonnage," defined as the sum of its [[shaft horsepower]] and [[gross tonnage]], as follows:
* If the power tonnage is 5,501 through 9,000, the first digit is "1".
* If the power tonnage 3,501 through 5,500, the first digit is "2."
* If the power tonnage is 2,001 through 3,500, the first digit is "3."
* If the power tonnage is 1,001 through 2,000, the first digit is "4."
* If the power tonnage is 501 through 1,000, the first digit is "5."
* If the power tonnage is 500 or less and the ship is at least {{convert|65|ft|m|abbr=off|sp=us}} long, the first digit is "6."<ref>{{cite web|url=http://www.corporateservices.noaa.gov/ames/administrative_orders/chapter_217/217-108.html|title=National Oceanic and Atmospheric Administration (NOAA) Home Page|first=US Department of Commerce, NOAA Office of the Chief Administrative Officer (OCAO). Elias|last=Abunassar|website=www.corporateservices.noaa.gov}}</ref>

The second and third digits are assigned to create a unique three-digit hull number.

== See also ==
* [[United States Navy 1975 ship reclassification]]
* [[List of hull classifications]] – same as this article but in alphabetical order
* [[List of ships of the United States Army]]
* [[Ship prefix]]
* [[Hull classification symbol (Canada)]]
* [[Pennant number]] for the British Commonwealth equivalent

== Notes ==
=== Explanatory notes ===
{{reflist|group=note}}

=== Wikilink footnotes ===
{{reflist|group=A}}

=== Citations ===
{{Reflist}}

== General and cited references ==
{{refbegin}}
* {{cite web|last1=Derdall |first1=Guy | last2=DiGiulian | first2=Tony | title=USN Ship Designations |date= 12 November 2016| url= http://www.navweaps.com/index_tech/index_ships_list.php | publisher= navweaps.com |access-date= 8 March 2017}}
* ''United States Naval Aviation 1910–1995, Appendix 16: U.S. Navy and Marine Corps Squadron Designations and Abbreviations''. U.S. Navy, c. 1995. Quoted in Derdall and DiGiulian, ''op cit''.
* {{cite web | url=http://www.moorefelines.com/documents/ACP113AFCall%20Sign%20Book%20For%20Ships.pdf | title=ACP 113 (AF) Call Sign Book for Ships | date=September 2004 | publisher=[[NATO]] | access-date=2008-07-02 | url-status=dead | archive-url=https://web.archive.org/web/20090227120003/http://www.moorefelines.com/documents/ACP113AFCall%20Sign%20Book%20For%20Ships.pdf | archive-date=27 February 2009 }}
* [https://web.archive.org/web/20101031033632/http://www.uscg.mil/history/faqs/Designations.asp USCG Designations]
* [https://web.archive.org/web/20100329212007/http://www.history.navy.mil/photos/shusn-no/spid-no.htm Naval History and Heritage Command Online Library of Selected Images: U.S. Navy Ships – Listed by Hull Number: "SP" #s and "ID" #s — World War I Era Patrol Vessels and other Acquired Ships and Craft]
* Wertheim, Eric. ''The Naval Institute Guide to Combat Fleets of the World, 15th Edition: Their Ships, Aircraft, and Systems''. Annapolis, Maryland: Naval Institute Press, 2007. {{ISBN|978-1-59114-955-2}}. {{ISSN|1057-4581}}.
{{refend}}

== Further reading ==
* Friedman, Norman. ''U.S. Small Combatants, Including PT-Boats, Subchasers, and the Brown-Water Navy: An Illustrated Design History''. Annapolis, Md: Naval Institute Press, 1987. {{ISBN|0-87021-713-5}}.

== External links ==
* [https://web.archive.org/web/20041016023831/http://www.nvr.navy.mil/class.htm Current U.S. Navy Ship Classifications]
* [https://web.archive.org/web/20120118095120/http://www.nvr.navy.mil/oldclass.htm U.S. Navy Inactive Classification Symbols]
* [https://web.archive.org/web/20070630220214/http://www.nvr.navy.mil/nvrservicecraft/index.htm U.S. Naval Vessels Registry (Service Craft)]
* [https://web.archive.org/web/20100910002034/http://www.nvr.navy.mil/nvrships/ U.S. Naval Vessels Registry (Ships)]
* [https://web.archive.org/web/20160922045534/http://www.nvr.navy.mil/SHIPS.html U.S. Naval Vessel Register (Current ships)]

{{US Navy navbox}}

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[[Category:Ships of the United States Navy]]
[[Category:Ship identification numbers]]
[[Category:Lists of ships of the United States|Hull classifications]]
[[Category:Ship naming conventions|United States]]
[[Category:Service vessels of the United States]]