Legio I Martia: one of the legions of the later Roman empire. Its name means that the legion was dedicated to the Roman war god Mars.
The only unambiguous evidence for the existence of this legion consists of one drawing of an inscription that is now lost. It mentions the building of a fortress in the province of Valeria (western Hungary) in forty-eight days in the year 371. It is likely that this legion is identical to the Martenses that are mentioned as part of the Illyrian field army in about 400 CE, and it is also likely that the legion was founded by Diocletian.
Possibly, this legion had the surname Victrix.