Antipope Constantine II (died 769?) was an antipope for over a year, 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.
Constantine was born into a noble Roman family in Nepi near Viterbo. He was one of four brothers, of which the most prominent was Toto of Nepi. Toto, the papal governor and self-styled "Duke" of Nepi, began to position himself to take advantage of the expected death of Pope Paul I, and elevate his own candidate onto the papal throne. Christophorus, the Primicerius of the notaries, forced Toto to take an oath to respect the traditional clerical method of papal elections. Toto, however, having retired to his estates in Nepi, with the help of Constantine and his other brothers collected troops from his duchy and other parts of Tuscany, in addition to arming a group of peasants to swell the numbers.
On 28 June, hearing that Pope Paul was on the verge of dying, Toto and his armed men forced their way into the city through the Gate of St. Pancratius. With Paul’s death, Toto made his way to the Basilica of the Apostles where the other members of the papal court and Roman nobility were gathering, and there Christophorus had everyone swear that they would all uphold each other’s rights during the upcoming election. However, as soon as the meeting had broken up, Toto’s armed retainers had assembled in his house at Rome and elected his brother Constantine as pope.
Since Constantine was still a layperson, he needed to be ordained deacon and priest and then consecrated as bishop in rapid succession. Although frowned upon by canon law, this approach was far from unknown at the time. Therefore, accompanied by a group of armed men, he was escorted to the Lateran Palace, where they attempted to force George, the Bishop of Praeneste, to ordain Constantine as a monk. George threw himself at Constantine’s feet, begging Constantine not to make him do this. However, Constantine and his supporters made it clear that he would be forced to, one way or another. George therefore performed the ceremony, ordaining Constantine as a monk. The next day, 29 June, Bishop George made Constantine a subdeacon followed immediately by his elevation to deacon. This contravened canon law, which required an interval between the giving of the major orders of at least one day.