Strathclyde (lit.

"Strath of the Clyde"), originally Brittonic Ystrad Clud or Alclud, is one of the early medieval kingdoms of the Celtic people called the Britons in the Hen Ogledd, the Brittonic-speaking parts of what is now southern Scotland and northern England.

The kingdom develops during the post-Roman period.

It is also known as Alt Clut, the Brittonic name for Dumbarton Rock, the medieval capital of the region.

It may have had its origins with the Damnonii people of Ptolemy's Geographia.The language of Strathclyde, and that of the Britons in surrounding areas under non-native rulership, is known as Cumbric, a dialect or language closely related to Old Welsh.

Place-name and archaeological evidence points to some settlement by Norse or Norse–Gaels in the Viking Age, although to a lesser degree than in neighboring Galloway.

A small number of Anglian place-names show some limited settlement by incomers from Northumbria prior to the Norse settlement.

Due to the series of language changes in the area, it is not possible to say whether any Goidelic settlement took place before Gaelic was introduced in the High Middle Ages.After the sack of Dumbarton Rock by a Viking army from Dublin in 870, the name Strathclyde comes into use, perhaps reflecting a move of the center of the kingdom to Govan.

In the same period, it is also referred to as Cumbria, and its inhabitants as Cumbrians.

During the High Middle Ages, the area is conquered by the Kingdom of Alba, becoming part of the new Kingdom of Scotland.

It remains a distinctive area into the 12th century.