Katherine Mortimer, Countess of Warwick (1314 – 4 August 1369) was the wife of Thomas de Beauchamp, 11th Earl of Warwick KG, an English peer, and military commander during the Hundred Years War. She was a daughter and co-heiress of Roger Mortimer, 1st Earl of March and Joan de Geneville, Baroness Geneville. Sometime before 1355, she became an important figure at the royal court of King Edward III.