M21

M21 or M-21 may refer to:

Roads

• M-21 highway (Michigan), a road connecting Flint and Grand Rapids
• M21 highway (Ukraine), a road in Ukraine

Military

• HMS M21, Royal Navy M15 class monitor; sunk in 1918
• M21 mine, an American circular anti-tank landmine
• M21 Sniper Weapon System, a sniper rifle based on the M14 rifle platform
• Zastava M21, a Serbian assault rifle

Other

• BMW M21, a 1983 2.4 L diesel straight-6 engine
• MSrE M-21, Hungarian aerobatics aircraft
• Lockheed M-21, an American reconnaissance drone carrier aircraft
• Messier 21, an open star cluster in the constellation Sagittarius
• M postcode area, M21 Chorlton-cum-Hardy, Firswood area of Manchester