Samuel Cooper (June 12, 1798 – December 3, 1876) was an American soldier. Born in the state of New York, he entered West Point at the age of 15 in 1813, graduated 36th in a class of 40 two years later, and was commissioned a second lieutenant of artillery in 1815. He was still serving in the United States Army in 1861, serving as the Army's Adjutant General. (In 1857 he had also briefly held the position of acting Secretary of War.) That year he declared his allegiance to be with the Rebels in the American Civil War despite being a Northerner. His reasons were personal: He had married into a prominent Virginian family and was a friend of Jefferson Davis.