First Legion may refer to:
The First Legion (1951 film) U.S. drama film Legio I (Ancient Rome), see List of Roman legions Legio I Adiutrix Legio I Armeniaca Legio I Germanica Legio I Iovia Legio I Isaura Sagittaria Legio I Italica Legio I Macriana liberatrix Legio I Maximiana Legio I Minervia Legio I Parthica 1st Legion Tercio "Great Captain Gonzalo Fernández de Córdoba", an infantry regiment in the Spanish Legion 1st Legions Infantry Division (Poland), an infantry division in the Polish army 1st Brigade, Polish Legions, an infantry brigade in the Austro-Hungarian army