Deira (
Old English:
Derenrice or
Dere) was a kingdom (559-664 AD) in
Northern England which probably emerged when Anglian warriors conquered the Derwent Valley in the third quarter of the fifth century. It extended from the
Humber to the
Tees, and from the sea to the western edge of the
Vale of York. It was the southern of the two kingdoms of Deira and
Bernicia which later merged to form the kingdom of
Northumbria.