pope from 1181 to 1185.

A Cistercian monk whom Pope Innocent II had made cardinal in 1141, Lucius was bishop of Ostia (consecrated 1159) and papal counsellor when elected on Sept. 1, 1181, to succeed Alexander III. As pope, Lucius was forced to leave Rome because the Romans had earlier declared their city a republic free from papal interference.

At the Synod of Verona in 1184, Lucius, in agreement with the Holy Roman emperor Frederick I Barbarossa, decreed the excommunication of heretics and their protectors; after ecclesiastical trial, heretics who refused to recant were transferred to civil authorities for punishment—usually death by burning. Lucius' synod activated the strict decrees of the third Lateran Council (1179); founded the medieval Inquisition to repress and punish heretics; and instigated the church's attack against the Cathari, a heretical sect that held that good and evil had separate creators. Apart from Frederick's promise to renew the Crusades, relations between Emperor and Pope were strained.