Philippe, comte de Noailles and later prince de Poix, duc de Mouchy, and duc de Poix à brevêt (27 December 1715–27 June 1794), was a younger brother of Louis, 4th duc de Noailles, and a more distinguished soldier than his brother. He served at Minden and in other campaigns, and was made a marshal of France in 1775, on the same day as his brother. He was long in great favor at court, and his wife was first lady of honor to Marie Antoinette, and was nicknamed by her Madame Etiquette. This court favor brought down punishment in the days of the French Revolution, and the old marshal and his wife were guillotined on 27 June 1794.

The comte de Noailles received the Spanish title of prince de Poix in 1729, and that of duc de Mouchy in 1747. In 1767 he received the additional French title of duc de Poix à brevêt. The title of prince de Poix passed to his son Charles-Adrien as a courtesy title on the latter's birth in 1747, and after the child's death later that year and the infant deaths of two further sons, came to rest on Noailles's successor, Philippe-Louis-Marc-Antoine.

Two of Noailles's three surviving sons, Philippe-Louis-Marc-Antoine and Louis-Marie, vicomte de Noailles, were members of the Constituent Assembly.