The Mitsubishi Saturn or 4G3 engine is series of overhead camshaft (OHC) straight-four internal combustion engines introduced by Mitsubishi Motors and saw first service in the 1969 Colt Galant.

An updated version with central-point electronic fuel injection was installed in Mirages and Lancers from 1986 on.

The engine has five main bearings, a cross flow head and a single down draught carburetor.

The GSR versions used two twin-barrel Mikuni-built Solex carburetors for a total of 110 hp (82 kW) (SAE).

A version with an early iteration of Mitsubishi's MCA lean-burn system (MCA-IIB), fulfilling the intermediate Japanese exhaust regulations for 1975, was called G32A.

For competition, a version of the 4G32 engine was made with a DOHC eight-valve cylinder head, and fitted with two twin-choke 40 mm (1.6 in) Solex sidedraft carburettors.

Effectively, the design was that of the standard Saturn four-cylinder block with two additional cylinders grafted on to replace the KE64.