Celestine II (born Teobaldo Boccapecci or Boccapeconai, Latin: Thebaldus Buccapecuc) was an antipope for one day, December 16, 1124. He was considered legitimate, but nonetheless submitted to the opposing pope, Honorius II.
He was made a Cardinal Deacon by Paschal II. He was selected as pope in a confused and chaotic election, in which Theobald and another cardinal, Saxo, were supported by the Pierleoni family. During the process of Celestine's investment, Robert Frangipani and a body of troops broke into the church and proclaimed Lamberto Cardinal Scannabecchi (a man of considerable learning) pope.
On Celestine's resignation, Scannabecchi became Honorius II.