Logan, John Alexander (1826–1886), a United States political leader and army officer. Logan served in both houses of Congress and in the Union Army, where he rose to the rank of major general. He was one of the most capable of the nonprofessional officers in the army.

Logan was born in Jackson County, Illinois. He was a lieutenant in the Mexican War and attended Shiloh College and Louisville University, receiving a law degree in 1851. He served in the House of Representatives as a Douglas Democrat from 1859 to 1861.

During most of the Civil War Logan served with the Army of the Tennessee, which he commanded briefly in 1864. He took part in the Siege of Vicksburg and the Battle of Atlanta, and was twice wounded. After the war he served in the House of Representatives as a Republican, 1866–71, and in the Senate, 1871–77 and 1879–86. He campaigned unsuccessfully for Vice President in 1884 as the running mate of James G. Blaine.

Logan was particularly active in veterans' affairs. He helped organize and was three times president of the Grand Army of the Republic. In 1868 he established May 30 as the date for Memorial Day. Logan wrote The Great Conspiracy (1886) and The Volunteer Soldier in America (1887).