Roman Emperor Constantine I, (Constantine the Great), was baptized in Nicomedia on May 22, 337. He was baptized on his deathbed, shortly before he died on May 22, 337 CE. A practice reflecting a common belief that baptism offered full spiritual cleansing only once.
Constantine had favored Christianity for most of his life and played a significant role in its legalization and spread. He was Baptized by Bishop Eusebius of Nicomedia Although some Catholic sources indicate he was Baptized by Pope Sylvester I in Rome. Most scholars dismiss it as a political effort to connect Constantine with an orthodox Roman bishop before the Great Schism.