Louis Philippe, comte de Ségur (10 December 1753 – 27 August 1830) was a French diplomat and historian.
Ségur was born in Paris, the son of Philippe Henri, marquis de Ségur and Louise Anne Madeleine de Vernon. He entered the army in 1769, served in the American War of Independence in 1781 as a colonel under Rochambeau.
In 1784 he was sent as minister plenipotentiary to Saint Petersburg, where he was received into the intimacy of the empress Catherine II and wrote some comedies for her theatre. At Saint Petersburg he concluded (in January 1787) a commercial treaty which was exceedingly advantageous to France. The same year he accompanied Catherine II in her journey to the Crimea. He returned to Paris in 1789.
Ségur took up a sympathetic attitude towards the Revolution at its outset and in 1791 was sent on a mission to Berlin, where he was badly received. After fighting a duel he was forced to leave Berlin, and went into retirement until 1801 when, at Bonaparte's command, he was nominated by the senate to the Corps Législatif. Subsequently he became a member of the council of state, grand master of the ceremonies, and senator, 1813. In 1814 Ségur voted for the deposition of Napoleon and entered Louis XVIII's Chamber of Peers. Deprived of his offices and functions in 1815 for joining Napoleon during the Hundred Days, he was reinstated in 1819, supported the Revolution of 1830, but died shortly afterwards in Paris.