5th Legion may refer to any of the following:
Roman legions Legio V Iovia, a Roman legion levied by Diocletian in the end of the 3rd century, and was still in service at the beginning of the 5th century. Legio V Alaudae ("Lark-crested Fifth Legion"), sometimes also known as Gallica, was a legion of the Imperial Roman army founded in 52 BC Legio V Macedonica, one of the original twenty-eight legions raised by Octavian
Other militaries Syrian Arab Army Fifth Corps also called the Fifth Legion Communist Fifth Regiment during the Spanish Civil War.