Antoine, Duke of Montpensier

French royal; youngest son of Louis Philippe I

Antoine, Duke of Montpensier (Antoine Marie Philippe Louis d'Orléans; 31 July 18244 February 1890), was a member of the French royal family in the House of Orléans. He was the youngest son of King Louis Philippe of France and his wife Maria Amelia Teresa of the Two Sicilies. He was styled as the Duke of Montpensier. He was born on 31 July 1824 at the château de Neuilly and died 4 February 1890 at Sanlúcar de Barrameda, Spain.

Antoine de Montpensier lived in Spain from 1848 when he and his family had to leave France after the Revolution of 1848. During the Spanish revolution of 1868, he supported the insurgents under Juan Prim against Queen Isabel II, his own sister in law. In 1870 he fought a duel against Infante Enrique, Duke of Seville, the brother of King Francisco, and killed him. Antoine was convicted and sentenced to one month in prison. On 16 November 1870 the Cortes voted for the next king and chose Amadeo of Savoy with 191 votes. Antoine only received 27 votes, and left Spain, only to return in 1874. His ambitions were fulfilled by his daughter Mercedes, who became Queen of Spain after her marriage to Alfonso XII, son of Isabella II. However, she died at the age of 18 without issue. Despite never reaching the throne, however, through cognates, he is an ancestor of all Spanish monarchs since Juan Carlos I. His great granddaughter Mercedes, Countess of Barcelona, was the mother of Juan Carlos, who assumed the throne in 1975 and later abdicated in favor of his son, Felipe VI in 2014.

The Duke of Montpensier was an early collector of photography. His collection consisted of dozens of albums and hundreds of early photographs, mainly of Spanish, French and British photographers. The collection was dispersed after his death.