John III (1469 – 14 June 1516), also known as Jean d'Albret, was the husband and co-monarch of Queen Catherine of Navarre. He was also the brother-in-law of Cesare Borgia, who was married to his sister, Charlotte d'Albret. He became King of Navarre by marriage to Queen Catherine and commanded an army of over 10,000 soldiers.
In 1506, when Cesare Borgia escaped the Castillo de la Mota, after having been imprisoned there since 1504, he sought help from King John III, who allowed Cesare to serve him for his experience in the military. In 1507, John III ordered Cesare to lead 10,000 of his men to the town of Viana, in order to take back the castle from the Count of Lerin. However, Cesare was killed during the siege of the castle by the Assassin Ezio Auditore da Firenze.