antipope from May to December 1012.

From the middle 10th to the early 11th century, Rome, and particularly the papacy, was chiefly ruled by the Crescentii, a powerful Roman family. After Pope Sergius IV's death (1012), the Crescentii uncanonically installed their candidate, Gregory, in the Lateran. A power struggle flared between the Crescentii and the Tusculani, a rival family, whose candidate was Pope Benedict VIII. Compelled to flee Rome, Gregory went to Germany, where he appealed his case to King St. Henry II (later Holy Roman emperor). Henry forced him to relinquish his claim before he performed any official acts, thus restoring Benedict. Gregory's subsequent history is unknown.