Gwendolen was a legendary queen of
Britain, as told by
Geoffrey of Monmouth in his pseudohistorical work
Historia Regum Britanniae (
History of the Kings of Britain; ). According to Geoffrey, she was the repudiated
queen of King
Locrinus until she defeated her husband in battle at the River Stour, the dividing line between Cornwall and Loegria, and took on the leadership of the
Britons herself, becoming their first recorded
queen regnant. Her victory and subsequent rise to fame as a righteous ruler shows how fractured Britain was at the time.