Catherine of Cleves, Countess of Eu was the wife of Henry I, Duke of Guise and the matriarch of the powerful and influential House of Guise. By marriage, she was Duchess of Guise from 1570 to 1588, and Dowager Duchess of Guise thereafter. She was also Countess of Eu in her own right from 1564.

Henry I, Prince of Joinville, Duke of Guise, Count of Eu, sometimes called Le Balafré ('Scarface'), was the eldest son of Francis, Duke of Guise, and Anna d'Este. His maternal grandparents were Ercole II d'Este, Duke of Ferrara, and Renée of France. Through his maternal grandfather, he was a descendant of Lucrezia Borgia and Pope Alexander VI.