Gregory VIII, born Mauritius Burdinus (Maurice Bourdin), was antipope from 10 March 1118 until 22 April 1121.
When Paschal II died on 24 January 1118, he was succeeded by Pope Gelasius II (1118-19). Henry V went to Rome but Gelasius II escaped to Gaeta and refused to meet the Emperor to discuss German affairs. Partly in reprisal the imperial party among the cardinals then annulled Gelasius II's election, and on March 1, 1118 Mauritius was proclaimed Pope, taking the name Gregory VIII. Gelasius II, at Capua, proceeded to excommunicate both Gregory VIII and Henry V on April 7, 1118.
After Gelasius II's death, when Calixtus II had been elected Pope in 1119, Henry V was induced to change papal allegiance, in the Concordat of Worms of 1122. Calixtus II entered Rome, and Gregory VIII left, going to Sutri, where he was in April 1121, when papal troops of Calixtus II closed up the city for eight days until its citizens surrendered antipope Gregory VIII. He was taken to Rome and imprisoned in the Septizonium. After having been moved in confinement from monastery to monastery, he finally died at La Cava, Salerno, some time after August 1137.