Aaron Vail (1796 – 1878) was an American diplomat. As a chargé d'affaires, he acted as the chief American officer in London in lieu of a Minister between April 4, 1832 and 1836; between the tenures of Martin Van Buren and Andrew Stevenson. He then became a Special Diplomatic Agent to Canada in 1838. On May 20, 1840, Vail then performed the same function as chargé d'affaires in Spain, being succeeded by Washington Irving on August 1, 1842. Born in New York, he died in Paris, France and was survived by his son, Aaron Vail II.