Jacques Hardouin-Mansart, comte de Sagonne (21 October 1677, Paris – 1762) was a French politician and soldier.
He was the second son and fifth and final child of the architect Jules Hardouin-Mansart (1646–1708) and Anne Bodin (1646–1738).
However, the marriage proved an unhappy one and in 1702 he took Guillemette Duguesny (later known as Madeleine) as his mistress - he had five children with her, but only two survived, the architects Jean Mansart de Jouy and Jacques Hardouin-Mansart de Sagonne.
Duguesny was then married to Jean Maury, a food clerk in Toulouse.
Duguesny used her two sons by Hardouin-Mansart to make a claim on his fortune right up until her death in 1753, which were opposed by his widowed mother Anne Bodin, the financier Claude Lebas de Montargis (husband of his sister Catherine-Henriette Hardouin-Mansart), then finally by Anne-Charlotte, marquise d'Arpajon, daughter of Claude and Catherine-Henriette.