M18 or M-18 may refer to:
Aircraft Messerschmitt M 18, an early German airliner Miles M.18, a Miles aircraft Mooney M-18 Mite, a low-wing monoplane PZL-Mielec M-18 Dromader, an agricultural and aerial-firefighting aircraft Myasishchev M-18, a design for a Soviet supersonic bomber with a variable-sweep wing
Firearms and military equipment M18 Claymore mine, an American anti-personnel landmine M18 Hellcat, an American tank destroyer used in World War II M18 smoke grenade, a colored smoke grenade M18 recoilless rifle, a late-World War II recoilless rifle SIG Sauer M18 pistol, a compact, carry sized SIG Sauer P320 used by the United States armed forces
Roads and highways M18 motorway (Great Britain) M18 motorway (Ireland) M-18 (Michigan highway) M18 (East London), a Metropolitan Route in East London, South Africa M18 (Cape Town), a Metropolitan Route in Cape Town, South Africa M18 (Johannesburg), a Metropolitan Route in Johannesburg, South Africa M18 (Pretoria), a Metropolitan Route in Pretoria, South Africa M18 (Port Elizabeth), a Metropolitan Route in Port Elizabeth, South Africa List of M18 roads
Other uses M18, a metric screw thread Messier 18, an open star cluster in the constellation Sagittarius M18 or M-18, Mara 18, Central American street gang Hope Municipal Airport, Arkansas, United States (FAA location identifier: M18) A line of 18-volt power tools manufactured by Milwaukee Electric Tool Corporation M18, a student club at the Bauhaus University, Weimar, Germany M18, a media content rating issued by the Infocomm Media Development Authority of Singapore Haplogroup M18 McLaren M18, a Formula 5000 racing car