Licinius I (Latin: Gaius Valerius Licinianus Licinius Augustus; c. 263-325) was a Roman emperor from 308 to 324. For most of his reign he was the colleague and rival of Constantine I; with whom he co-authored the Edict of Milan that granted official toleration to Christians in the Roman Empire. He was finally defeated at the Battle of Chrysopolis; before being executed on the orders of Constantine I.