Epsilon is General Motors' mid-size front-wheel drive automobile platform. The architecture was a multi-division project of GM North America, Opel and Saab, and debuted in the 2002 Opel Vectra and 2003 Saab 9-3. Since this platform falls squarely in the center of the worldwide automobile market, GM plans to produce a great many Epsilon vehicles with over a dozen variations. As of 2005, it was GM's highest volume worldwide platform. Even after the dissolution of the GM/Fiat partnership, both companies retain the rights to continue developing Epsilon-derived models.

The General Motors G platform automobile platform designation was used for front-wheel drive full-sized and luxury cars between 1995 and 2011.