Augustine of Canterbury (birth unknown, died May 26, 604 (traditional) or 605 (Thorn)) was the first Archbishop of Canterbury, sent to Ethelbert of Kent, Bretwalda of England by Pope Gregory the Great in 597. He was accompanied by Laurence of Canterbury, the second archbishop.

In 596, Augustine was praepositus (prior) of the monastery of Saint Andrew, founded by Pope Gregory I, and was sent by Gregory at the head of forty monks to preach to the Anglo-Saxons. They lost heart on the way and Augustine went back to Rome from Provence and asked that the mission be given up. The pope, however, commanded and encouraged them to proceed, and they landed on the Island of Thanet in the spring of 597.

Ethelbert's wife Bertha, daughter of Charibert, one of the Merovingian kings of the Franks, had brought a chaplain with her (Liudhard) and either built a church or restored a church in Canterbury from Roman times and dedicated it to St. Martin of Tours, a major patronal saint for the Merovingian royal family. Ethelbert himself was a pagan, but allowed his wife to worship God her own way. Probably under influence of his wife, Ethelbert asked Pope Gregory I to send missionaries.

Ethelbert permitted the missionaries to settle and preach in his town of Canterbury and before the end of the year he was converted and Augustine was consecrated bishop at Arles. At Christmas 10,000 of the king's subjects were baptized.

Augustine sent a report of his success to Gregory with certain questions concerning his work. In 601 Mellitus, Justus and others brought the pope's replies, with the pallium for Augustine and a present of sacred vessels, vestments, relics, books, and the like. Gregory directed the new archbishop to ordain as soon as possible twelve suffragan bishops and to send a bishop to York, who should also have twelve suffragans,- a plan which was not carried out, nor was the primatial see established at London as Gregory intended. Augustine consecrated Mellitus Bishop of London and Justus Bishop of Rochester.

More practicable were the pope's mandates concerning heathen temples and usages: the former were to be consecrated to Christian service and the latter, so far as possible, to be transformed into dedication ceremonies or feasts of martyrs, since "he who would climb to a lofty height must go up by steps, not leaps" (letter of Gregory to Mellitus, in Bede, i, 30).

Augustine reconsecrated and rebuilt an old church at Canterbury as his cathedral and founded a monastery in connection with it. He also restored a church and founded the monastery of St. Peter and St. Paul outside the walls.

His attempts to effect a union with the old British Church in Wales failed.