Lucius Decidius Saxa (died 40 BC), sometimes mistaken as Decidus, was a Roman general in the 1st century BC. He was born in Spain, but perhaps of Italian origin. In 49 BC he fought as follower of Julius Caesar in Spain against an army of Pompey. In 44 BC he was tribune of the people and after the assassination of the dictator he went over to Mark Antony. At the beginning of 43 BC Antony was besieged in Mutina and was assisted by Decidius Saxa. In 42 BC, after the founding of the second Triumvirate, Saxa was, together with Gaius Norbanus Flaccus, appointed by Mark Antony to lead the advance force of eight legions into Thrace before the Battle of Philippi.