Answer
Otto IV reigned as the Holy Roman Emperor from 1209 to 1218. He was the son of Henry the Lion, Duke of Saxony, and Matilda, daughter of King Henry II of England. Otto was crowned emperor in Rome in 1209, but his reign was marked by conflict with Pope Innocent III. In 1215, Innocent excommunicated Otto and supported the rival claimant to the throne, Frederick II, son of Henry VI.