Jonathan Mayhew Wainwright II (July 27, 1821 – January 1, 1863) was an officer in the United States Navy during the American Civil War, who was killed in action during the Battle of Galveston.

[1] He commanded the Harriet Lane, Admiral David Dixon Porter's flagship in Farragut's fleet, in the Battle of Forts Jackson and St. Philip, and took part in operations below Vicksburg.

He was killed in action when his ship was attacked and captured by Confederate forces under the command of General John Bankhead Magruder during the Battle of Galveston on January 1, 1863.

[1][7][8] He was reportedly personally killed by Confederate naval commander Leon Smith, and a valuable signal book was taken from his corpse.

[13] Together, they had four children:[13][14] His grandson, Jonathan Mayhew Wainwright IV (1883–1953), was a general during World War II.