Major Robert Anderson (1805-1871) was a Union Army officer in the American Civil War.

Born in Kentucky, Anderson remained loyal to the Union. He is notable for being the commanding officer of Fort Sumter in the harbor of Charleston, South Carolina at the time it was bombarded by forces of the Confederate States of America. The Confederate attack was led by P.T.G Beauregard, who was Anderson's student at West Point. The attack began April 12, 1861 and continued until Anderson, badly outnumbered and outgunned, surrendered the fort on April 14, 1861. The battle began the American Civil War.

Anderson took the fort's 33-star flag with him to New York City, where he participated in a Union Square patriotic rally that is thought to have been the largest public gathering in North America up to then. Anderson then went on a highly successful recruiting tour of the North before taking a leave of absence due to ill health. In time, he was promoted to the rank of major general.

At the conclusion of the war, Maj. Gen. Anderson returned to Charleston and, four years to the day after lowering the 33-star flag in surrender, raised it in triumph over the recaptured but badly-battered Fort Sumter during ceremonies there.

Anderson's brother Charles Anderson served as Governor of Ohio from 1865-1866. His nephew Thomas M. Anderson was a brigadier general who fought in the Spanish-American War and Philippine-American War.