Count of Guise and Duke of Guise (/ɡwiːz/ GWEEZ, French: [ɡ(ɥ)iz]) were titles in the French nobility.
Originally a seigneurie, in 1417 Guise was erected into a county for René, a younger son of Louis II of Anjou.
While disputed by the House of Luxembourg (1425–1444), the county was ultimately retained by the House of Anjou and its descendants, passing in 1520 to the cadet branch of the ducal House of Lorraine that became known as the House of Guise, headed by Claude of Lorraine. In 1528, the county was elevated to a dukedom and peerage of France for him. The Dukes of Guise and their sons played a prominent role in the French Wars of Religion, during which they were the leaders of the ultra-Catholic faction.
This dukedom became extinct in 1688, and the lands attached to it passed to the Princess Palatine Anne, a great-granddaughter of Charles of Lorraine-Guise, Duke of Mayenne – although she was not the heiress in strict primogeniture, that being the Duke of Mantua. The dukedom was recreated for Anne and her husband, Henri Jules de Bourbon, Prince of Condé in 1704.
On the extinction of the Bourbon-Condé family in 1830, the Guise dukedom was inherited by the House of Orléans, descendants of Anne's granddaughter Louise Henriette de Bourbon, Duchess of Orleans. Louis Philippe of Orléans having become King of the French in 1830, henceforth the title Duke of Guise was used as a courtesy title for members of this family after it was deposed and went into exile in 1848, firstly for three sons of Prince Henri, Duke of Aumale, and then for Prince Jean, son of Robert d'Orléans, Duke of Chartres. In 1926, Jean, Duke of Guise became the Orléanist claimant to the throne of France as "Jean III".