Catherine of Bourbon (7 February 1559 – 13 February 1604) was a Navarrese regent princess. She was the daughter of Queen Joan III and King Anthony of Navarre. She ruled the principality of Béarn in the name of her brother, King Henry III of Navarre, from 1576 until 1596. Early life Catherine was born on 7 February 1559 to Jeanne d'Albret, Queen of Navarre and her co-ruler, Antoine of Bourbon. She was named after her godmother, the French queen Catherine de' Medici. Jeanne converted to Calvinism a year after Catherine's birth and declared it the official religion of the Kingdom of Navarre. Antoine, conversely, remained a Catholic and turned against his wife and threatened to divorce her. He died fighting for the Catholic cause on 17 November 1562. Catherine was with her mother and elder brother, Henry, as they fought for the Protestant cause. The Queen died on 9 June 1572, and Catherine's custody was assigned to Catherine de' Medici and Charles IX. During the St. Bartholomew's Day Massacre, Catherine and her brother were forced to convert to Catholicism. After the death of Charles IX in 1574, the new king, Henry III, considered marrying Catherine. She almost married James VI of Scotland, and her brother sent ambassadors to Edinburgh to advocate the marriage, including Claude de l'Isle, François de Civille, and Jérôme Groslot. Political service Catherine's brother, successor of Queen Joan III, was generally absent from the principality. After his escape from captivity in 1576, he entrusted Catherine with the government of Béarn. She served almost continuously as regent until 1596, where among her other responsibilities, she, a staunch Protestant, hosted Antonio Perez, a famous Spanish Catholic refugee from King Philip II. After the accession of her brother to the French throne, in 1589, she was created Duchess of Albret and Countess of Armagnac. Appointed by her brother to sit on his Council as a representative of French Protestant interests in 1598, she set about persuading the Huguenots to agree to the Edict of Nantes. Marriage As part of the treaty of Saint-Germain-en-Laye between Henry IV and Charles III, Duke of Lorraine, it was agreed that Catherine should marry Charles' elder son, Henry (1563–1624). The marriage agreement was signed on 13 July 1598. However, Catherine was a confirmed Calvinist, who refused to convert to Roman Catholicism, whilst her husband was a devout Catholic, and a former member of the Holy