Duke of Orléans (French:Duc d'Orléans) was a title reserved for French royalty, first created during the 14th century. Known as princes of the blood (princes du sang), the title of Duke of Orléans was given, when available, to the oldest brother of the king. Thus, they formed a collateral line of the French royal family, with an eventual right to succeed to the throne should more senior princes of the blood die out.
During the period of the ancien régime the holder of the title often assumed a political role. The Orléans branch of the House of Valois came to the throne with Louis XII (15th century). Louis Philippe II, fifth Duke of Orléans, contributed to the destruction of the ancient regime. At the head of a retrospectively named 'Orleanist' faction centred on the Palais Royal, he contested the authority of his cousin Louis XVI in the adjacent Louvre. His son would eventually ascend the throne in 1830 following the July Revolution as Louis-Philippe I, King of the French. The descendants of the family are the Orléanistpretenders to the French throne, and the title has been used by several members of the House. The holder of the title held the style of Serene Highness.