Caesar Flavius Valerius Aurelius Constantinus Augustus (27 February c. 272 - 22 May 337), commonly known in English as Constantine I, Constantine the Great, or (among Eastern Orthodox, Oriental Orthodox and Byzantine Catholic Christians) Saint Constantine (pronounced /ˈkɒnstəntaɪn/ or /ˈkɒnstəntiːn/), was Roman emperor from 306, and the sole holder of that office from 324 until his death in 337. Best known for being the first Christian Roman emperor,[notes 1] Constantine reversed the persecutions of his predecessor, Diocletian, and issued (with his co-emperor Licinius) the Edict of Milan in 313, which proclaimed religious tolerance throughout the empire. The Byzantine liturgical calendar, observed by the Eastern Orthodox Church and Eastern Catholic Churches of Byzantine rite, lists both Constantine and his mother Helena as saints. Although he is not included in the Latin Church's list of saints, which does recognize several other Constantines as saints, he is revered under the title "The Great" for his contributions to Christianity.
Constantine also transformed the ancient Greek colony of Byzantium into a new imperial residence, Constantinople, which would remain the capital of the Eastern Roman Empire for over one thousand years.