M18

M18 or M-18 may refer to:

In transportation:
* M18 motorway, a motorway in Yorkshire, England
* M-18 (Michigan highway), a state highway in Michigan
* Miles M.18, a Miles aircraft
* Mooney Mite M-18, a low-wing monoplane
* PZL-Mielec M-18 Dromader, an agricultural and aerial-firefighting aircraft
* Russian Route M18, a highway that extends from Saint Petersburg to Murmansk in Russia

In science:
* Messier 18 (M18), an open star cluster in the constellation Sagittarius

In firearms and military equipment:
* M18 Claymore, an American anti-personnel landmine
* M18 Hellcat, an American tank destroyer used in World War II
* M18 colored smoke grenade, a smoke grenade
* M18 Recoilless Rifle, A late-World War II recoilless rifle

In crime:
* M18 or M-18, Mara 18