D21
D21 may refer to:
Vehicles
Aircraft
- Dewoitine D.21, a French fighter
- Fokker D.XXI, a Dutch fighter
- Lockheed D-21, an American reconnaissance drone
- Salmson D21 Phrygane, a French utility aircraft
Ships
- Template:Ship, a Nueva Esparta-class destroyer of the Venezuelan Navy
- Template:HMS, a County-class destroyer of the Royal Navy
- Template:HMS, a Q-class destroyer of the Royal Navy
- Template:HMS, a Ruler-class escort aircraft carrier of the Royal Navy
- Template:HMS, a W-class destroyer of the Royal Navy
- Template:Ship, a Fletcher-class destroyer of the Spanish Navy
Surface vehicles
- Allis-Chalmers D21, an American tractor
- Nissan D21, a Nissan Datsun pickup truck
- LNER Class D21, a class of British steam locomotives
Other uses
- Arriflex D-21, a digital motion picture camera
- Chondroma
- D21 road (Croatia)
- D21 – Janeček method, an electoral system
- D21, a computer from Datasaab
- D-21 Special, a guitar made by Martin Guitar