M121 or M-121 may refer to: M121/A1 155mm Cartridge, a U.S. Army chemical artillery shell; M-121 (bomb), a World War II bomb; M121 mortar carrier, the United States designation for the Soltam TT6; M-121 highway (Michigan), a road connecting Zeeland and Grandville; Mauboussin M.121 Corsaire Major, a 1921 French trainer and touring aircraft