Bretwalda (also brytenwalda and bretenanwealda, sometimes capitalised) is an Old English word. The first record comes from the late 9th-century Anglo-Saxon Chronicle. It is given to some of the rulers of Anglo-Saxon kingdoms from the 5th century onwards who had achieved overlordship of some or all of the other Anglo-Saxon kingdoms. It is unclear whether the word dates back to the 5th century and was used by the kings themselves or whether it is a later, 9th-century, invention. The term bretwalda also appears in a 10th-century charter of Æthelstan. The literal meaning of the word is disputed and may translate to either 'wide-ruler' or 'Britain-ruler'.
The rulers of Mercia were generally the most powerful of the Anglo-Saxon kings from the mid 7th century to the early 9th century but are not accorded the title of bretwalda by the Chronicle, which had an anti-Mercian bias. The Annals of Wales continued to recognise the kings of Northumbria as "Kings of the Saxons" until the death of Osred I of Northumbria in 716.