Alexandre de Vendôme (19 April 1598 – 28 February 1629) was the third illegitimate child, and second illegitimate son, of Henry IV of France and his mistress Gabrielle d'Estrées.

He was a prior of the Langue of France of the Order of Saint John of Jerusalem.

Baptized in Saint-Germain-en-Laye on 13 December 1598,[1] he was governor of Caen[2] from birth throughout his life and entered the Order of Saint John of Jerusalem in 1604.

King Louis XIII, his half-brother, appointed him to lead an embassy to Pope Paul V at Rome in October 1614.

In 1626 alongside his brother César, Duke of Vendôme and half-brother Gaston, Duke of Orléans, he participated in the Chalais conspiracy, directed against Cardinal Richelieu, who was the Prime Minister of his half-brother, King Louis XIII.