Constantine I  "the Great" was Emperor of the Roman Empire from 306-337CE. He was born in what is now Serbia. He was a great supporter of Christianity, sponsoring the council of Nicea. He was not baptized until he was on his deathbed, but this was not unusual for Christians of the time.

"Religion is regarded by the common people as true, by the wise as false, and by the rulers as useful."
Seneca, Roman Philosopher, mid 1st century CE