Antipope Constantine II was an antipope

Antipope

An antipope is a person who opposes a legitimately elected or sitting Pope and makes a significantly accepted competing claim to be the Pope, the Bishop of Rome and leader of the Roman Catholic Church. At times between the 3rd and mid-15th century, antipopes were typically those supported by a...

 in 767

767

Year 767 was a common year starting on Thursday of the Julian calendar. The denomination 767 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.-Africa:* The Kharijite Berbers of Tlemcen and Tiaret...

 and 768

768

Year 768 was a leap year starting on Friday of the Julian calendar. The denomination 768 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.- Europe :* Pepin the Short , king of the Franks since...

.

He was born in Nepi

Nepi

Nepi is a town and comune in Italy in the province of Viterbo, region of Lazio. The town lies 30 km southeast of the city of Viterbo and about 13 km southwest from Civita Castellana....

 near Viterbo

Viterbo

See also Viterbo, Texas and Viterbo UniversityViterbo is an ancient city and comune in the Lazio region of central Italy, the capital of the province of Viterbo. It is approximately 80 driving / 80 walking kilometers north of GRA on the Via Cassia, and it is surrounded by the Monti Cimini and...

, a scion, along with his three brothers, of noble Roman family.

During the last days of the Pope Paul I

Pope Paul I

Pope Paul I was pope from May 29, 757 to June 28, 767. He first served as a Roman deacon and was frequently employed by his brother, Pope Stephen II, in negotiations with the Lombard kings....

 in June, his brother Toto of Nepi

Toto of Nepi

Toto was the self-styled duke of Nepi, the leading magnate of Etruria, who staged a coup d'état in Rome in 767. He became Duke of Rome for a year until his death...

 and a body of Tuscans placed him upon the See of Peter when he was still a layman.
It was therefore necessary that he be ordained and then elevated to papal office in rapid succession: although frowned upon by canon law

Canon law

Canon law is the body of laws & regulations made or adopted by ecclesiastical authority, for the government of the Christian organization and its members. It is the internal ecclesiastical law governing the Catholic Church , the Eastern and Oriental Orthodox churches, and the Anglican Communion of...

, this approach was far from unknown at the time. Constantine notified his election to the Frankish King, Pepin the Short, but the latter never replied.

In spring 768

768

Year 768 was a leap year starting on Friday of the Julian calendar. The denomination 768 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.- Europe :* Pepin the Short , king of the Franks since...

 he was deposed and killed by Lombards

Lombards

The Lombards , also referred to as Longobards, were a Germanic tribe of Scandinavian origin, who from 568 to 774 ruled a Kingdom in Italy...

, when prisoner in the monastery of San Saba

San Saba (Rome)

San Saba is an ancient basilica church in Rome, Italy. It lies on the so-called Piccolo Aventino, which is an area close to the ancient Aurelian Walls next to the Aventine and Caelian Hill....

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