Legio I Iovia (devoted to Jupiter) was a Roman legion, levied by Emperor Diocletian (284-305), possibly together with II Herculia, to guard the newly created province of Scythia Minor. The cognomen of this legion came from Diocletian's attribute Iovianus, "similar to Jupiter".
According to Notitia Dignitatum, at the beginning of the 5th century I Iovia was still in its camp on the Danube.