Martin Reuben Merritt Wallace (September 29, 1829 – March 6, 1902) was a Union Army officer from October 12, 1861 to November 3, 1864 during the American Civil War. He was colonel of the 4th Regiment Illinois Volunteer Cavalry when he was mustered out of the volunteers on November 3, 1864. In recognition of his service, in May 1866, he was nominated for appointment and confirmed to the grade of brevet brigadier general of volunteers, to rank from March 13, 1865.