Licinius I (Latin: Gaius Valerius Licinianus Licinius Augustus; c. 263–325) was a Roman emperor from 308 to 324. For the majority 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.