Pendragon Castle is a ruin located in Mallerstang Dale, Cumbria, south of Kirkby Stephen, and close to the hamlet of Outhgill (at grid reference NY781025).

It stands above a bend in the River Eden, overlooked by Wild Boar Fell to the south-west and Mallerstang Edge to the east.

[1] According to legend, the castle was built by Uther Pendragon, father of King Arthur, who is said to have unsuccessfully tried to divert the river to provide its moat,[2] as is recalled in a well-known local couplet: Let Uther Pendragon do what he can,Eden will run where Eden ran.Uther (if he was indeed a real person) was possibly a 5th-century chieftain who led resistance to the invading Anglo-Saxons.

One of its most notable owners was Sir Hugh de Morville, Lord of Westmorland, one of the four knights who murdered St Thomas Becket in 1170.

After the latter attack it remained an uninhabitable ruin until it passed into the hands of Lady Anne Clifford, who rebuilt it in 1660, also adding a brewhouse, bakehouse, stables and coach-house.