Prince Louis Thomas of Savoy (German: Ludwig Thomas von Savoyen, Graf von Soissons; Italian: Luigi Tommaso di Savoia; 15 December 1657 – 14 August 1702) was a Count of Soissons and Prince of Savoy.

After the premature death of his father in 1673 and the flight of his mother to Brussels due to her involvement in the notorious Poison affair, Louis Thomas and his siblings remained in Paris and were entrusted to the care of their grim grandmother Marie de Bourbon and their aunt Princess Louise of Savoy, Margravine of Baden Baden.

Since the family had fallen out of favour with the king because of Olympia Mancini's behaviour, Louis-Thomas inherited the titles of his fathers, but not his offices and thus his income.

His sisters and his daughters remained unmarried, his brothers Louis-Jules (1660–1683) and Emanuel-Philibert (1662-1676), and his son Thomas Emmanuel, pursued their military careers outside France, as did his other two brothers that had initially been directed to ecclesiastical careers, Philip (1659–1693), who died fighting for the Venetians against the Turks, and Prince Eugene of Savoy, who became one of the most famous generals in the service of the House of Habsburg.

[4][5] On 18 August Louis was killed by a French bomb at the Siege of Landau at the onset of the War of the Spanish Succession.