Constantine I ( 27 February 272 â `` 22 May 337 AD ) was a powerful general who reigned over the Roman Empire as emperor , until his death . Flavius Valerius Aurelius Constantinus ( c. 27 February 272 â `` 22 May 337 ) , commonly known as Constantine I , Constantine the Great , or Saint Constantine ( or ) , was Roman Emperor from 306 to 337 .