GM C platform, also known as the C-Body, was a front wheel drive (FWD) automobile platform used by General Motors' Cadillac, Buick and Oldsmobile divisions for their full-sized automobiles from 1985 through 1996, sharing unibody construction, transverse engine configuration, rack and pinion steering and four-wheel independent suspension.

C-Bodies used, V6 or V8 engines, GM's TMH440 transaxle (initially), unibody construction — and all had been aerodynamically refined, with the Oldsmobile achieving a .383 drag coefficient.

GM's C platform and H platform were largely identical, sharing the same 110.8 in wheelbase, most bodywork, interior details, glass and engines. Manufacture began with the C platform in late 1983, first at two purpose-built plants, Wentzville Assembly and Orion Assembly — later moving to Lansing Car Assembly as well as Flint and Willow Run assembly plants.

Significantly shorter, narrower, lighter and more fuel-efficient than the platform they replaced, the C Platform vehicles were noted for having nearly the same key interior dimensions as their predecessors and a much more nearly flat passenger compartment floor^[1] — albeit with thinner seats and dramatically less upper tumblehome, locating windshield as well as side glass closer to passengers.^[1]

Introduced in early 1984, the models were marketed as the Oldsmobile Ninety-Eight (11th gen), Buick Electra (6th gen) and Cadillac Deville (6th gen) and Fleetwood (1985-90)..

Cadillac would later introduce C Body models with a 113.8 in wheelbase. Most C-body vehicles were ultimately replaced with cars on the related G, H, and K platform designations.

The Cadillac Series 75 limousine briefly made its return on this platform, stretched by 23.6" to a wheelbase of 134.4". Cadillac used the platform though 1993; Buick heavily revised the Electra, becoming the first generation Buick Park Avenue (1991-1996), while still using the C Platform; and Oldsmobile marketed C Platform derivatives through 1990, notably the Oldsmobile Touring Sedan.

The H platform and C platform were largely identical, sharing the same 110.8 in wheelbase, most bodywork, interior details, glass and engines.