Pierre Philippe Jean Marie d'Orléans (November 4, 1845 – July 17, 1919) was Duke of Penthièvre and a grandson of French king Louis Philippe I. Declining a proposal to marry into the Brazilian royal family, he chose a naval career and fathered two children without marrying. Prince Pierre was an officer in the Union and French Navies and a global traveler.

Prince Pierre d'Orléans was the son of François d'Orléans, Prince of Joinville and his wife, Princess Francisca of Brazil. On his father's side, he was the grandson of the French king Louis Philippe I. On his mother's side he was the grandson of Pedro I & IV, Emperor of Brazil and King of Portugal and the Algarves, for whom he was named.

Princess Françoise of Orléans (14 August 1844 – 28 October 1925), the older sister of Prince Pierre d'Orléans, is an ancestor of the three Orléanist pretenders to the throne of France since 1926: Jean III (her son), Henri VI and Henri VII. Pierre d'Orléans also had a younger sister who was stillborn (30 October 1849).

Although he never married, Prince Pierre d'Orléans had two children with Angélique Marie Augustine Lebesgue (d. 1881), a married woman:

Born in the Château de Saint-Cloud in 1845, Prince Pierre was expelled from France with his family when the Revolution overthrowing his grandfather, King Louis Philippe I, broke out in 1848. Prince Pierre had a happy childhood as a refugee in England with most of the other members of the House of Orléans, despite the uncertainty of life in exile. The education of Prince Pierre, his sister and cousins was overseen by his father in England and organized at first by a tutor. In 1859 Prince Pierre and his cousin, Prince Ferdinand, Duke of Alençon, left for Scotland to study at the prestigious Royal High School in Edinburgh.

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