M51

M51 or M-51 may refer to:

• M-51 (Michigan highway), a state highway in Michigan
• M51 highway (Russia)
• M51 (Cape Town), a Metropolitan Route in Cape Town, South Africa
• M51 Skysweeper, an anti-aircraft gun
• M51 MACI mine
• M51 SLBM, a French nuclear ballistic missile
• BMW M51, a 1991 straight-6 Diesel engine
• Sherman M-51, an Israeli modification of American M4 Sherman tank
• Eidgenössischer Stutzer 1851, a historical service rifle of the Swiss Army
• Messier 51, a spiral galaxy also known as the Whirlpool Galaxy
• Samsung Galaxy M51, a smartphone released in 2020