Queen Gwendolen was the wife of King Locrinus of the Britons until she defeated him in battle and took on the leadership of Britain herself according to Geoffrey of Monmouth.

Gwendolen was the daughter of Corineus of Cornwall and was married to Locrinus, with whom she had one son, Maddan. Locrinus was in love with Estrildis, the daughter of the king of Germany whom he rescued from Humber the Hun, though. When Corineus finally died, Locrinus left Gwendolen and married Estrildis. Gwendolen fled to Cornwall and built up and army. She met Locrinus in battle and defeated him.

Following Locrinus's death, Gwendolen took the throne and led in the manner her father had in Cornwall. She ordered the murder of Estrildis and her daughter Habren and named the river they were thrown into Severn (Habren). She reigned peacefully for fifteen years after Locrinus's death until she abdicated in favor of her son, Maddan. She lived the remainder of her life in Cornwall.

At the time of her death, Samuel was judge in Judea, Aeneas Silvius was ruling Alba Longa, and Homer was gaining fame in Greece.