Deira was an early British kingdom, established sometime in the sixth century by Germanic, Anglian settlers. The name is probably derived from the Brythonic Dewyr, the name of the preceding Romano-British kingdom which was based in what is modern Humberside.
Location
Based north east coast of England, or roughly the modern counties of Yorkshire and Humberside; that is the territory between the river Tees and the Humber with its capital at York.
Kings of Deira
Ruled by Bernicia (604-616)
Interregnum, Deira overrun by Cadwallon ap Cadfan of Gwynedd
Ruled by Bernicia (634-644)
Sub-kings appointed by Oswiu and Ecgfrith of Bernicia
History
It is Aelle ( or Ælla or variants thereof) who is the reputed founder of the kingdom of Deira and comes equipped with the standard Germanic genealogy showing descent from Woden (1). It must be presumed that after establishing control of Dewyr proper, Aelle must have continued to conquer and absorb the Romano-British kingdom of Caer Ebrauc (based on the Roman city of Eboracum or modern York), as York is generally given as the capital of the kingdom of Deira.
Aelle was succeeded by his son Aethelric, but Aethelric soon fell victim to the territorial ambitions of Aethelfrith king of neighbouring Bernicia who defeated and killed Aethelric in 604. Fortunately Aelle's younger son Edwin managed to escape into exile, returning in 616 with the assistance of Raedwald, king of East Anglia to re-establish the Deiran royal line.
When Edwin fell victim to the combined forces of Cadwallon ap Cadfan and Penda of Mercia the pendulum eventually swung the other way; (Osric's brief attempt to establish himself is scarcely worth mentioning), one of Aethelfrith's sons
Oswine was really the last independent king of Deira, who managed to seize some degree of power and autonomy despite being subordinate to the Bernician king Oswiu. After Oswine's assassination in 651, Deira really became nothing more than a province of Bernician Northumbria. Subsequent kings were essentially appointees from the junior ranks of the Bernician royal line.
Aethelwald was the son of Oswald and therefore Oswiu's nephew; Alhfrith and Aelfwine were both sons of Oswiu. Even this proved problematic as both Aethelwald and Alhfrith (for various reasons) utilised Deira as a power base for insurrection. After the death of Aelfwine, (killed at the battle of the Trent against Mercia), even this pretence was abandoned and Deira became fully absorbed within Northumbria.
NOTES
(1) the son of Iff, son of Usfrey, son of Wilgis, son of Westerfalcon, son of Seafowl, son of Sebbald, son of Sigeat, son of Swaddy, son of Seagar, son of Waddy, son of Woden.