The Battle of Mobile Bay of August 5, 1864, was a naval and land engagement of the American Civil War in which a Union fleet commanded by Rear Admiral David G. Farragut, assisted by a contingent of soldiers, attacked a smaller Confederate fleet led by Admiral Franklin Buchanan and three forts that guarded the entrance to Mobile Bay: Morgan, Gaines and Powell. Farragut's order of "Damn the torpedoes! Four bells. Captain Drayton, go ahead! Jouett, full speed!" became famous in paraphrase, as "Damn the torpedoes, full speed ahead!"

The battle was marked by Farragut's seemingly-rash but successful run through a minefield that had just claimed one of his ironclad monitors, enabling his fleet to get beyond the range of the shore-based guns. This was followed by a reduction of the Confederate fleet to a single vessel, ironclad CSS Tennessee.

Tennessee did not then retire, but engaged the entire Northern fleet. Tennessee's armor enabled her to inflict more injury than she received, but she could not overcome the imbalance in numbers. She was eventually reduced to a motionless hulk and surrendered, ending the battle. With no Navy to support them, the three forts also surrendered within days. Complete control of lower Mobile Bay thus passed to the Union forces.

Mobile had been the last important port on the Gulf of Mexico east of the Mississippi River remaining in Confederate possession, so its closure was the final step in completing the blockade in that region. This Union victory, together with the capture of Atlanta, was extensively covered by Union newspapers and was a significant boost for Abraham Lincoln's bid for re-election three months after the battle. This battle concluded as being the last naval engagement in the state of Alabama in the war. It would also be Admiral Farragut's last known engagement.