
The Lateran Council of 769 was a synod held in the Basilica of St. John Lateran to rectify perceived abuses in the papal electoral process which had led to the elevation of the antipopes Constantine II and Philip. It also condemned the rulings of the Council of Hieria. It is perhaps the most important Roman council held during the 8th century.
The selection of the pope, the bishop of Rome and supreme pontiff of the Catholic Church, prior to the promulgation of In nomine Domini in 1059 varied throughout history. Popes were often putatively appointed by their predecessors or by political rulers. While some kind of election often characterized the procedure, an election that included meaningful participation of the laity was rare, especially as the popes' claims to temporal power solidified into the Papal States. The practice of papal appointment during this period would later result in the putative jus exclusivae, i.e., the claimed but invalid right to veto the selection that Catholic monarchs exercised into the twentieth century.
An antipope is a person who claims to be Bishop of Rome and leader of the Roman Catholic Church in opposition to the officially elected pope. Between the 3rd and mid-15th centuries, antipopes were supported by factions within the Church itself and secular rulers. While modern claimants to the papacy still take place, they are rarely given serious consideration by either the public or the Church.
Antipope Constantine II 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.
Antipope Philip was an antipope who held office for just one day, on 31 July 768.