Map of the Roman empire in AD 125, under emperor Hadrian, showing the Legio IV Flavia Felix, stationed on the Danube river at Singidunum (Belgrade, Serbia), in Moesia Superior province, from AD 82 until the 5th centuryAntoninianus minted under Carausius. On the reverse, the lion, symbol of the legion, and the legend LEG IIII FL.
Legio IV Flavia Felix ("Lucky Flavian Fourth Legion"), was a legion of the Imperial Roman army founded in AD 70 by the emperor Vespasian (r. 69–79) from the cadre of the disbanded Legio IV Macedonica. The legion was active in Moesia Superior in the first half of the 5th century. The legion symbol was a lion.