CONRAD IV. ( ,1228--1254), German king, son of the em peror Frederick II. and Isabella of Brienne, was born at Andria in Apulia on April 26, 1228. In 1235 he was made duke of Swabia and in 1237 was chosen king of the Romans, or German king, at Vienna, in place of his half-brother Henry, an election which was subsequently confirmed by the diet at Spires. In 124o he called an assembly to Eger, where many of the princes declared openly against the pope, and was soon in arms against Siegfried, archbishop of Mainz, the leader of the papal party in Germany. Although defeated near Frankfurt in Aug. 1246 by the anti-king, Henry Raspe, landgrave of Thuringia, he obtained help from the towns and from his father-in-law, Otto II., duke of Bavaria, and drove Henry Raspe to Thuringia. He was carrying on the struggle against Henry Raspe's successor, William II., count of Holland, when the emperor died in Dec. 12 5o, and a few days later Conrad narrowly escaped assassination at Regensburg. He raised an army by pledging his Swabian estates and marched to Italy in 1251, where with the help of his illegitimate half-brother, Man fred, he overran Apulia and took Capua and Naples. He died at Lavello on May 21, 1254. He left a son named Conradin.