antipope from 1118 to 1121.

A Benedictine educated at the abbey of Cluny, he was made bishop of Coimbra, Port., in 1098. While archbishop of Braga, Port. (consecrated 1111), he quarrelled with Archbishop Bernard of Toledo, Castile, and was suspended by Pope Paschal II in 1114. Later he was cleared and became part of the papal court.

When the Holy Roman emperor Henry V invaded Italy in 1116, because Paschal denied him the right to grant clerical offices to ecclesiastics, the Pope fled to Benevento and sent Gregory to confer with Henry. Gregory, however, defected to Henry's cause and was excommunicated. On Paschal's death, Henry set Gregory up as antipope against Pope Gelasius II, but Gregory was excommunicated by Gelasius (1118) and by Pope Calixtus II (1119). Imprisoned in a series of monasteries, he died in exile in 1140.