Strathclyde (străth´klīd´) [Gaelic,=Clyde valley], one of several early medieval Celtic or Welsh kingdoms in present-day S Scotland and N England. Strathclyde was in SW Scotland. To the east was the kingdom of Manaw Gododdin and to the south, Rheged. Little is known of the history of Strathclyde and the other Welsh (Cumbrian) kingdoms. The origin of Strathclyde is uncertain, but there is evidence that the kingdom had been consolidated by the middle of the 5th cent. In 945, King Edmund of Wessex defeated Strathclyde and awarded it to King Malcolm of Scotland; however, Scotland did not permanently absorb the kingdom until the 11th cent. The reason for the disappearance of the ancient British language and culture in the kingdoms is not definitely known. Dumbarton was the principal town in Strathclyde.
See J. Rhys, Celtic Britain (1882); P. H. Blair, An Introduction to Anglo-Saxon England (1962); F. M. Stenton, Anglo-Saxon England (3d ed. 1971).