M103

M103 or M-103 may refer to:


 * M103 heavy tank, an American heavy tank
 * M103 (New York City bus), a bus route in Manhattan
 * M-103 (Michigan highway), a state highway in Michigan
 * Mercedes-Benz M103 engine
 * Messier 103, an open star cluster in the constellation Cassiopeia
 * Motion 103, also known as M-103, a motion in the House of Commons of Canada
 * M103 railway (Croatia), a railway line in Croatia