The Second Battle of Fort Wagner, also known as the Second Assault on Morris Island or the Battle of Fort Wagner, Morris Island, was fought on July 18, 1863, during the American Civil War. Union Army troops commanded by Brig. Gen. Quincy Gillmore launched an unsuccessful assault on the Confederate fortress of Fort Wagner, which protected Morris Island, south of Charleston Harbor. The battle came one week after the First Battle of Fort Wagner. Although a Confederate victory, the valor of the Black Union soldiers in the battle was hailed, which had long-term strategic benefits in encouraging more African-Americans to enlist allowing the Union to employ a manpower resource that the Confederacy could not emulate for the remainder of the war.

During the American Civil War, the United States Army, the land force that fought to preserve the collective Union of the states, was often referred to as the Union Army, the Grand Army of the Republic, the Federal Army, or the Northern Army. It proved essential to the restoration and preservation of the United States as a working, viable republic.