Justus (occasionally Iustus; dies on November 10 between 627 and 631) is the fourth Archbishop of Canterbury.

He is sent from Italy to England by Pope Gregory the Great, on a mission to Christianize the Anglo-Saxons from their native paganism, probably arriving with the second group of missionaries dispatched in 601.

Justus becomes the first Bishop of Rochester in 604, and attends a church council in Paris in 614.

Following the death of King Æthelberht of Kent in 616, Justus is forced to flee to Gaul, but is reinstated in his diocese the following year.

In 624, Justus becomes Archbishop of Canterbury, overseeing the dispatch of missionaries to Northumbria.

After his death he is revered as a saint, and has a shrine in St Augustine's Abbey, Canterbury.