Eleutherius of Tournai was a 5th and 6th-century Frankish bishop, traditionally recognized as the first leader of the church in Tournai. Born in Tournai during the reign of Childeric I, he served as a presbyter and courtier alongside his lifelong friend, Medardus. Following the reorganization of the church hierarchy in northern Gaul by Remigius, Eleutherius was appointed to his episcopal see. He is remembered for his efforts to combat Arianism and for his role in the early Christian history of the region.