The Mitsubishi 3B2 engine is a family of all-alloy three cylinder engines developed by Mitsubishi Motors, first produced in December 2005 at the company's Mizushima powertrain facility in Kurashiki, Okayama, for introduction in their 2006 Mitsubishi i kei car. All engines developed within this family have aluminum cylinder block and head, double overhead camshafts, four valves per cylinder, and MIVEC continuous variable valve timing.

The Mitsubishi i is a kei car from automaker Mitsubishi Motors, first released in January 2006, twenty eight months after its debut at the 2003 Frankfurt Motor Show. It is the first four-door automobile since the 1960s to employ a "rear midship" setup with the engine behind the passengers, in an attempt to improve safety and interior space without enlarging the overall exterior.