The 8th Regiment Illinois Volunteer Cavalry was a cavalry regiment that served in the Union Army during the American Civil War. The regiment served the duration of the war, and was the only Illinois cavalry regiment to serve the entire war in the Army of the Potomac. They also aided in the hunt for John Wilkes Booth and served as President Lincoln's honor guard while he lay in state under the rotunda. Lincoln gave them the nickname of "Farnsworth's Abolitionist Regiment" when he watched them march past the White House.