Offa was King of Essex. He was heir apparent when in 709, he went on a pilgrimage to Rome along with Cenred, King of Mercia. He would succeed to the kingdom, appearing as co-king with Swæfred. He was the son of Sighere, who had died in 688.
In his Historia ecclesiastica gentis Anglorum, Bede described him as "a youth of most lovely age and beauty, and most earnestly desired by all his nation to be their king. He, with like devotion, quit his wife, lands, kindred and country, for Christ and for the Gospel, that he might receive an hundredfold in this life, and in the world to Come life everlasting. He also, when they came to the holy places at Rome, receiving the tonsure, and adopting a monastic life, attained the long wished-for sight of the blessed apostles in heaven."
A charter related to land in Warwickshire (S64) is attributed to him, although in it he is described as King of Mercia rather than Essex. This may be an inaccurate copy based on an authentic charter by Cenred of Mercia. There is a (probably authentic) lost charter (S1784) in which Offa grants land in Hemel Hempstead to the bishop of London.
He was succeeded by Saelred of Essex.