Marcus Fabius Ambustus (fl. 360–351 BC) was a statesman and general of the Roman Republic. He was the son of Numerius Fabius Ambustus. He served as consul three times: in 360, 356, and 354 BC. His consulships occurred during a time in which Rome was reasserting itself following its defeat at the hands of the Gauls in the Battle of the Allia of 387 BC. He defeated the Hernici in 356, and Tibur in 354, earning a triumph for the latter victory. He further succeeded against the Falisci, but was defeated by Tarquinia.