Lucius III, né Ubaldo Allucingoli (1097 – November 25, 1185), was pope from September 1, 1181 to November 25, 1185.

A native of the independent republic of Lucca, he joined the Cistercian order. He was named cardinal-priest of Santa Prassede by Pope Innocent II and cardinal-bishop of Ostia and Velletri by Pope Adrian IV. He was one of the most influential cardinals under Pope Alexander III.

After being elected pope, he lived at Rome from November 1181 to March 1182, but dissensions in the city compelled him to pass the remainder of his pontificate in exile, mainly at Velletri, Anagni and Verona.

He disputed with the emperor Frederick I the disposal of the territories of the late Countess Matilda of Tuscany. The controversy over the succession to the inheritance of the Countess had been left unsettled by the peace of 1177, and the Emperor Frederick proposed in 1182 that the Curia should renounce its claim, receiving in exchange two-tenths of the imperial income from Italy, one-tenth for the pope and the other tenth for the cardinals. Lucius consented neither to this proposition nor to another compromise suggested by Frederick the next year; nor did a personal discussion between the two potentates at Verona in Oct., 1184, lead to any definite result.

Meantime other causes of disagreement appeared, in the pope's refusal to comply with Frederick's wishes as to the regulation of German episcopal elections which had taken place during the schism, and especially as to the contested election to the see of Treves in 1183.

In pursuance of his anti-imperial policy, he declined finally in 1185 to crown Henry VI as Frederick's destined successor, and the breach between the empire and the Curia became wider on questions of Italian politics.

In November 1184 he held a synod at Verona which condemned the Cathars, Paterines , Waldensians and Arnoldists , and anathematized all those declared as heretics and their abettors.

In 1185 preparations began for the Third Crusade in answer to appeals of Baldwin IV of Jerusalem. Before they were completed, Lucius died in Verona.