Margaret de Mortimer was a notable figure in medieval England, born around 1310. She was the daughter of Roger de Mortimer, the 1st Earl of March, and Joan de Geneville. Margaret played a significant role in the political landscape of her time, particularly through her marriage to John of Gaunt, the Duke of Lancaster, which strengthened alliances among the English nobility. Margaret's lineage connected her to various influential families, making her a key player in the power dynamics of the 14th century. She was the mother of several children, including Henry IV of England, further solidifying her family's prominence in English history.