Otto IV of Germany was a Holy Roman Emperor who reigned from 1209 to 1215. Born in 1175, he was a member of the Welf dynasty and the grandson of Henry the Lion. Otto IV became king of Germany in 1198, following a power struggle with Philip of Swabia. His reign was marked by conflicts with the Pope and rival factions within the empire. Otto IV sought to strengthen his authority but faced challenges, including the rise of Frederick II, who would later succeed him. Otto IV's reign ended when he was deposed in 1215, leading to a decline in his influence.