Deira (/ˈdaɪrə, ˈdɛərə/ DY-rə, DAIR-ə;[1] Old Welsh/Cumbric: Deywr or Deifr; Old English: Derenrice or Dere) was an area of Post-Roman Britain, and a later Anglian kingdom.

[4][5] Following the Roman withdrawal from Britain a number of successor kingdoms rose in northern England, reflecting pre-Roman tribal territories.

[6] It is not known if Deira was ever an independent Brythonic kingdom, and no British king has been identified with the area from the surviving genealogies, poems or chronicles.

However the area was subject to the same fractious inheritance traditions and changing power dynamic (following the Roman withdrawal) that allowed Elmet and Bernicia to become independent hereditary kingdoms in the early fifth century.

[7][8] The kingdom, which was previously ruled by a British dynasty, was probably created in the third quarter of the fifth century when Anglian warriors invaded the Derwent Valley.