Constantinus (d. April 9, 715) was Pope from 708 to 715. He was a Syrian by birth and was consecrated pope on March 25, 708. He was eager to assert the supremacy of the papal see.

From October 710 to October 711 he went to Constantinople at the request of the Emperor, Justinian II. The Emperor wished to resolve the disagreements between the Eastern and Western Churches which had arisen out of the Quinisext Council of 692. The negotiations were conducted by Gregory, the future Pope Gregory II. A degree of compromise was reached. However, shortly after Constantine's return to Rome, Justinian was killed by mutinous troops, in November 711.

The new emperor, Philippicus Bardanes was an adherent of monothelitism, rejected the arrangements of the Sixth General Council, and demanded Constantine's support of the view that Christ had only one will. Constantine rejected this, and the Emperor's name was excluded from official documents. As the exarch (the Imperial representative in Italy) attempted to enforce the Imperial presence there were clashes, but Constantine was able to calm the situation.

Philippus was overthrown in June 713, and his successor, Anastasius II communicated to the Pope his support for the Sixth General Council.