Stephen V, 1239–72, king of Hungary (1270–72), son and successor of Bela IV. As a child he was named duke of Transylvania, and in 1259 he was made duke of Styria. After the loss (1260) of Styria to Ottocar II of Bohemia, Stephen returned to Transylvania and married a Cuman princess. He rebelled against his father and in 1262 forced him to share the kingdom. After invading (1268) Bulgaria, Stephen took the title king of Bulgaria. He secured alliances by marrying his children into the ruling families of Naples, Byzantium, and other powers, and in 1271 he repulsed an invasion by Ottocar. He was succeeded by his son, Ladislaus IV.