Antipope Constantine II (Latin: Constantinus; died c. 769) was a Roman prelate who claimed the papacy from 28 June 767 to 6 August 768. He was overthrown through the intervention of the Lombards and tortured before he was condemned and expelled from the Church during the Lateran Council of 769.
Upon the death of Pope Paul I various factions contended to secure the appointment of their respective candidates as pope. Constantine, although a layman, was supported by a group of Tuscan nobles, led by his brother. They secured his election by force of arms. The following spring, local authorities, with Lombard support, succeeded in deposing him. The Lombards then attempted to install their own candidate, a priest named Philip.