Saint Sergius I, the Pope,  was a powerful leader who defended the authority of the Bishop of Rome and resisted imperial interference in Church affairs. His reign strengthened the Western Church and preserved its traditions.

Saint Sergius I, the eighty-fourth pope of the Church, was one of the most powerful popes in the history of the Church. His actions were aimed at strengthening the authority of the Bishop of Rome over the Western Church. Pope Sergius tried to prevent Emperor Justinian II from exerting more influence and power over the Western Church. He also resisted the pressure on the Pontiff to act according to the emperor's wishes in the East, and did not give in to such moves.

The steps taken by the pope to block these moves were many. In AD 666, for the first time since the elevation of the diocese to an autonomous status, Pope Sergius consecrated Damian as the new metropolitan of the Archdiocese of Ravenna. He bestowed the pallium on the new Archbishop of Canterbury, and restored Bishop Wilfrid as Bishop of York. Pope Sergius recognized Willibrod's missionary work in Frisia and later consecrated him as Metropolitan of Frisia. It was during his reign that the See of Aquileia, which had been in disunity with the Church, was united with Rome. This ended the schism that began in AD 559.

In AD 692, Emperor Justinian II asked Pope Sergius to ratify the decisions of the council he had convened, apparently as a follow-up to the Second and Third Councils of Constantinople. Pope Sergius refused the emperor's request.

The council convened by Emperor Justinian II in AD 692 was known as the Trullan Council, as it met in the dome of the emperor's palace in Constantinople. The council excluded bishops from the Western Church, ignored Western canon law, and banned many customs and traditions that existed in the Western Church, such as clerical celibacy and fasting on Saturdays during Lent. It also revised the twenty-eighth canon of the Council of Chalcedon, giving Constantinople equal status with Rome.

When Emperor Justinian realized that Pope Sergius was not ready to accept the council's actions and decisions, he sent his commander of the guard to arrest the pope and bring him to Constantinople. However, the royal troops in and around Ravenna opposed this attempt and subdued the emperor's captain. The pope's plea for the captain's life saved him. The disgraced emperor was deposed and exiled in AD 695.

During his reign, Pope Sergius restored the basilicas of St. Peter and St. Paul, as well as other churches in Rome. Similarly, the remains of Pope Leo the Great, who had been buried in an inconspicuous tomb, were transferred to an ornate tomb in the main part of St. Peter's Basilica. A skilled musician, Pope Sergius introduced the practice of singing the prayer "Agnus Dei" in the form of a hymn during the Mass and on the four major feast days of the Blessed Virgin Mary.

Pope Sergius, who led the Holy Catholic Church for nearly a decade and a half, passed away on September 8, AD 701. His mortal remains were laid to rest in St. Peter's Basilica.