Philippe Henri, marquis de Ségur (20 January 1724 - 3 October 1801) was a marshal of France.
Born in Paris, son of Henri François, comte de Ségur, and his wife Philippe Angélique de Froissy, he was appointed to the command of an infantry regiment at eighteen, and served under his father in Italy and Bohemia. He was wounded at Roucoux in Flanders in October 1746, and lost an arm at Lauffeld in 1747. In 1748 he succeeded his father as lieutenant-general of Champagne and Brie; he also received in 1753 the governorship of the county of Foix.
The ability which he showed in the government of Franche-Comté in 1775 led in 1780 to his appointment as minister of war under Necker. He created in 1783 the permanent general staff, and made admirable regulations with regard to barracks and military hospitals; and though he was officially responsible for the reactionary decree requiring four quarterings of nobility as a condition for the appointment of officers, the scheme is said not to have originated with him and to have been adopted under protest. On 13 June 1783 he became a marshal of France. He resigned from the ministry of war in 1787.
He married in Paris on 3 February 1749 Louise Anne Madeleine de Vernon (Paris, 1729 - Paris, 12 March 1778), daughter of Alexandre de Vernon and Anne du Vivier, and had two sons:
Alexandre Marie Léonor de Saint-Mauris de Montbarrey
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Louis Charles-Auguste le Tonnelier, baron de Breteuil