The siege of Fort Gaines, Alabama, occurred between August 3 and 8, 1864, during the American Civil War.

Union forces under the command of Major Genereral Gordon Granger landed on Dauphin Island, about 7 miles from Fort Gaines, on August 3, and moved against Fort Gaines guarding the western edge of Mobile Bay.

Granger's force numbered about 1,500,[3] while 818 troops under the command of Confederate Colonel Charles D. Anderson garrisoned the fort.

The Union fleet had 199 guns to attack with, while the Confederates only held 26 within the walls of Fort Gaines.

[4] Anderson, believing he could not hold out against a combined attack by the Union army and navy, chose to surrender the fort on August 8.