The Subaru FA engine is a gasoline boxer-4 engine used in Subaru and Toyota automobiles. It is a derivative of the FB engine, with efforts to reduce weight while maintaining durability as the main design goals. Although the FA and FB engines share a common platform, the FA shares very little in dedicated parts with the FB engine, with a different block, head, connecting rods, and pistons.

The Subaru FB engine is the third and current generation of gasoline boxer-4 engine used in Subaru automobiles, and was announced on 23 September 2010. It follows the previous generation EJ-series engine which was introduced in 1989 and the first generation EA-series which was introduced in 1966. By increasing piston stroke and decreasing piston bore, Subaru aimed to reduce emissions and improve fuel economy, while increasing and broadening torque output compared to the EJ-series.