César de Bourbon, Légitimé de France (3 June 1594 – 22 October 1665) was the son of Henry IV of France and his mistress Gabrielle d'Estrées, and founder of the House of Bourbon-Vendome. He held the titles of 1st Duke of Vendôme, 2nd Duke of Beaufort and 2nd Duke of Étampes, but is also simply known as César de Vendôme. Through his daughter, Élisabeth de Bourbon, César was a great-great-great-grandfather of Louis XV of France, merging thereafter to the French royal line. César de Bourbon is also an ancestor of Juan Carlos I of Spain, of Albert II, King of the Belgians, of Henri, Grand Duke of Luxembourg, and of Vittorio Emanuele, Prince of Naples, a pretender to the Italian throne.

Born at the Château de Coucy in the Picardy region of France; his parents had started their affair in 1591 and César had been the couple's first child. He was legitimised in 1595, and was created the first Duke of Vendôme by his father in 1598. The Duchy of Vendôme had been owned by the Bourbon dynasty since 1393, at that point being a County then being raised by Louis XII of France to a Duchy. In the same year, he was engaged to Françoise de Lorraine (1592–1669), "...one of the richest heiresses in France".

In 1598, César was created Duke of Vendome in his own right. One year later he also inherited the titles of Duke of Beaufort and Duke of Étampes upon the death of his mother, who died as a result of a miscarriage in Paris.

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