| Louis Phélypeaux | |
| Office2: | Acting Secretary of State for War |
| Death Place: | Paris, Isle-de-France, Kingdom of France |
| Birth Place: | Paris, Isle-de-France, Kingdom of France |
| Birth Date: | 18 August 1705 |
| Successor2: | Louis François de Monteynard |
| Predecessor2: | Étienne François de Choiseul |
| Term2: | 24 December 1770 – 4 January 1771 |
| Monarch2: | Louis XV |
| Monarch1: | Louis XV |
| Honorific Suffix: | Count of Saint-Florentin & Duke of La Vrillière |
| Successor1: | Emmanuel-Armand de Richelieu |
| Predecessor1: | Étienne François de Choiseul |
| Term1: | 24 December 1770 – 6 June 1771 |
| Office1: | Minister for Foreign Affairs |
| Successor: | Guillaume-Chrétien de Lamoignon de Malesherbes |
| Predecessor: | Jean-Frédéric Phélypeaux |
| Term: | 1749 – 1775 |
| Office: | Secretary of State of the Maison du Roi |
| Honorific Prefix: | Most High and Most Potent Lord |
Louis Phélypeaux (18 August 1705 - 27 February 1777) Count of Saint-Florentin, Marquis (1725) and Duke of La Vrillière (1770), was a French politician.
Son of Louis Phélypeaux, Marquis de La Vrillière, and Françoise de Mailly-Nesle (1688–1742), he succeeded his father as Secretary of State for Protestant Affairs, with responsibility for Huguenots. Appointed minister for the Department of the Maison du Roi by Louis XV in 1749, he held the post until 1775, setting a record for ministerial service. He was named to the Order of the Holy Spirit, where he served as chancellor. After the dismissal of Choiseul in December 1770, he served as Foreign Minister until June 1771. His use of lettres de cachet in the La Chalotais case was controversial and he resigned his ministerial posts in 1775.
In 1724 he married Amélie Ernestine de Platen (d. 1752). He had Chalgrin design the Hôtel de Saint-Florentin. This later passed to Talleyrand and to James Mayer de Rothschild, and is now part of the American Embassy, Paris.