General Motors Diesel Division was a unit of General Motors founded in 1938. GMDD's Canadian operations were renamed as Diesel Division of General Motors of Canada Limited in 1975.

The company was a manufacturer of diesel engines, diesel locomotives, transit buses and military vehicles.

The engine making unit later became Detroit Diesel and sold to DaimlerChrysler AG in 2000 (formerly part of General Motors Diesel). The locomotive unit (Electro-Motive Diesel) was acquired by private investors, the transit bus divisions were purchased by TMC in the U.S. and MCI in Canada (the latter entities were sold to form Nova Bus in 1993), and the GM Defense unit was purchased by General Dynamics.