The Duchy of Cantabria (Spanish: Ducado de Cantabria, Cantabrian: Ducáu de Cantabria) was a march created by the Visigoths in northern Spain to watch their border with the Cantabrians and Basques. Its precise extension is unclear in the different periods, but seems likely that it included Cantabria, parts of Northern Castile, La Rioja, and probably western areas of Biscay and Álava.