Æthelwealh (fl. c. 660 – c. 685) (also written Aedilualch, Aethelwalch, Aþelwold, Æðelwold, Æþelwald, or Ethelwalch) was the first historical king of Sussex. Æthelwealh became the first Christian king of Sussex and was king when Sussex was converted to Christianity in 681. In 661, Æthelwealh received the territories of the Meon Valley in modern-day Hampshire, and the Isle of Wight from his godfather, Wulfhere, king of Mercia. Æthelwealh was killed in around 685 by Cædwalla, at the time a prince of the Gewisse tribe of modern-day Oxfordshire, who had been operating as bandit in Sussex.All known information about him comes from brief mentions in Eddius's The Life of Bishop Wilfrid, Bede's Ecclesiastical History of England, and The Anglo-Saxon Chronicle. Æthelwealh was the third recorded ruler of the South Saxons in Sussex.
A case can be made (Slaughter) that Æthelwealh was installed by Penda in 645, when Cenwalh was driven out of his kingdom by Penda for divorcing the latter's sister. Cenwalh had deprived Penda's sister of her queenly status, and a just recompense when Penda invaded Wessex would have been for him to have deprived Cenwalh of the kingdom in Sussex.Æthelwealh became a Christian while in Mercia where the King of Mercia, King Wulfhere, sponsored his baptism. At this time the people of Sussex were pagans.
In 661, Wulfhere gave Æthelwealh the territories of Meonwara and the Isle of Wight.
Æthelwealh's queen was Eafe (also written Eabae or Ebba), the daughter of Eanfrith (Eanfrid or Eanfridi), a ruler of the Christian Hwicce people.Wilfrid, the exiled bishop of York, came to Sussex in 681 and converted the people to Christianity with King Æthelwealh's approval. Æthelwealh gave Wilfrid land in Selsey where he founded Selsey Abbey. Wilfrid, however met with Caedwalla a prince of the Gewisse, then operating as a bandit in Sussex , and came to a mutual agreement to advance one another's interests. According to Bede, in 686, Cædwalla invaded South Saxon territory and killed Æthelwealh. Cædwalla was then driven out by two of Æthelwealh's ealdormen, Berhthun and Andhun. When Cædwalla became King of the West Saxons, the following year, he conquered Sussex and appears to have appointed an Ecgwald as a sub-regulus (on cartulary evidence).His name means "noble foreigner".According to tradition, Cædwalla invaded Sussex and was met by Æthelwealh at a point in the South Downs just southeast of Stoughton, close to the border with Hampshire, and it was here that Æthelwealh was defeated and slain. According to the same tradition, Æthelwealh lies buried in the southern barrow of the group that marks the spot.