Oslac ealdorman (or earl) of York from around 963 to 975. His territory included but may not have been limited to the southern half of Northumbria. His background is obscure because of poor source documentation. The latter has facilitated disagreement amongst historians regarding his family and ethnicity.
He may have been the first ealdorman of southern—as opposed to a united—Northumbria, though an alternative tradition puts the division of Northumbria into two ealdormanries after his death. Little is known of his career as ealdorman, except for a legend that he escorted the Scottish king Kenneth II to the English royal court, and that he was expelled from England in 975. His life is unattested after this. He had one known son, but it is not clear if that son ever succeeded him.