Ursacius, Bishop of Singidunum, fl. 357-371

Ursacius (fl. 335–346) was the bishop of Singidunum (the ancient city which was to become Belgrade), during the middle of the 4th century. He played an important role during the evolving controversies surrounding the legacies of the Council of Nicaea and the theologian Arius, acting frequently in concert with his fellow bishops of the Diocese of Pannonia (or "Illyria"), Germinius of Sirmium and Valens of Mursa. Found at various times during their episcopal careers staking positions on both sides of the developing theological debate and internal Church politicking, Ursacius and his fellows were seen to vacillate according to the political winds.