The FA 58 (French: Fusil Automatique Type 58) was a prototype French battle rifle designed in 1958 and produced in very small numbers in prototype form only by the Manufacture d'armes de Saint-Étienne. One of a number of automatic weapon prototypes designed by MAS during the 1950s and 1960s, the FA 58 was an unsuccessful attempt at replacing the MAS 49 in service.
The FA 58 was one of a number of automatic weapon prototypes designed by engineers at MAS as a potential weapon to replace the MAS 49 rifle in service; it was felt that there was a need for the French to standardize their weapons with the then-newly introduced 7.62×51mm NATO cartridge, and to reduce or avoid reliance on other countries for equipment the weapon had to be of French manufacture.
The weapon was never actually submitted to military trials. While the rifle's attempt at replacing the MAS 49 was without success, the work done on the FA 58 eventually culminated in the design of the FA-MAS Type 62.
The FA 58's action was heavily based on the MAS 49, being gas-operated with a tilting bolt. The FA 58's charging handle was on the left of the receiver.