M109 is a self-propelled 155 mm howitzer.
M109 may also refer to:
Military HMS Bangor (M109), a Sandown-class minehunter Messerschmitt Bf 109, a German World War 2 fighter aircraft M109 shop van, a variant of a M35 2½ ton cargo truck
Other uses M-109 highway (Michigan), a state highway in Michigan, US Messier 109 (M109), a spiral galaxy in the constellation Ursa Major Suzuki Boulevard M109R, a motorcycle
See also Barrett XM109, an anti-materiel weapon