Pope Gregory VII
Gregory VII (born Hildebrand of Sovana (c. 1015 – May 1085 AD) was Pope from 22 April 1073 to his death in 1085.
One of the great reforming popes, he is perhaps best known for the part he played in the Investiture Controversy, his dispute with Henry IV, Holy Roman Emperor that affirmed the primacy of papal authority and the new canon law governing the election of the pope by the College of Cardinals. He was also at the forefront of developments in the relationship between the emperor and the papacy during the years before he became pope. He was the first pope in several centuries to rigorously enforce the Western Church’s ancient policy of celibacy for the clergy and attacked the practice of simony.
He excommunicated Henry IV three times. Consequently, Henry IV would appoint Antipope Clement III to oppose him in the political power struggles between the Catholic Church and his empire. Hailed as one of the greatest of the Roman pontiffs after his reforms proved successful, Gregory VII was, during his own reign, despised by some for his expansive use of papal powers.
Wikipedia for background, portrait.