USS Choctaw was a large (1,004-ton) steamer built for the merchant service, but acquired by the Union Navy during the second year of the American Civil War.

She was purchased by the United States Army on 27 September 1862 and converted into an ironclad ram by Edward Hartt, then transferred to commissioned into the United States Navy at St. Louis, Missouri on 23 March 1863 with Lieutenant Commander Francis M. Ramsay in command.

From 23 April 1863, until the end of the war, Choctaw operated in the Mississippi River and its tributaries.

Between 29 April and 1 May 1863, she stood up the Yazoo River for a feigned attack on Haynes' Bluff, Mississippi, designed to prevent the Confederates from reinforcing Grand Gulf.

Remaining in the Yazoo, she took part in attacks with the Union Army which led to the destruction of Confederate works at Haynes' Bluff and the burning of the navy yard and ships lying there, at Yazoo City, between 18 and 23 May.