Martin Davis Hardin (June 26, 1837 – December 12, 1923) was a brigadier general in the Union Army during the American Civil War.

Hardin graduated from West Point in the Class of 1859, and was an aide to Robert E. Lee in the hanging of John Brown soon after.

He was mustered out of the volunteer service in June 1864 but returned to active duty on July 2 with an appointment to brigadier general.

Hardin spent his last years in the famous "Union Generals' House" at 20 Valencia Street in St. Augustine, Florida (saved from a proposed demolition by Flagler College in the 1980s through the concerted action of local history lovers).

[2] His widow honored him by building a chapel (complete with a statue of St. Martin) on the grounds of the Mission of Nombre de Dios in St. Augustine.