Otto IV 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 emperor after a power struggle with Philip of Swabia, marking a significant period in the political landscape of medieval Europe. His reign was characterized by conflicts with the Pope and various German princes. Otto IV sought to strengthen imperial authority but faced challenges that ultimately led to his excommunication in 1210. He was eventually defeated and lost his title, dying in 1218.