Pope Innocent III (Latin:Innocentius III; 1160 or 1161 – 16 July 1216) reigned from 8 January 1198 to his death. His birth name was Lotario dei Conti di Segni, sometimes anglicised to Lothar of Segni.

Pope Innocent was one of the most powerful and influential popes. He exerted a wide influence over the Christian regimes of Europe, claiming supremacy over all of Europe's kings. Pope Innocent was central in supporting the Catholic Church's reforms of ecclesiastical affairs through his decretals and the Fourth Lateran Council. This resulted in a considerable refinement of Western canon law. Pope Innocent is notable for using interdict and other censures to compel princes to obey his decisions, although these measures were not uniformly successful. Innocent called for Christian crusades against Muslim Spain and the Holy Land, as well as the Albigensian Crusade against the Cathars in southern France.