Lucius Fairchild (December 27, 1831 – May 23, 1896) was an American politician, army general, and diplomat. He served as the tenth Governor of Wisconsin and as U.S. Minister to Spain.
General Fairchild, as a Private in 1858, enlisted in a Wisconsin volunteer militia known as the "governor's guard". Under his guidance the militia was titled Company K, 1st Wisconsin volunteers and by 1861, was serving in the Civil War at Falling Waters against the "Stonewall Brigade" of General Thomas J. Jackson. In August 1861, Fairchild was appointed captain in the 16th U.S. Infantry as well as major of the 2nd Wisconsin Volunteer Infantry Regiment. The 2nd Wisconsin served in the brigade commanded by General William T. Sherman until the general reorganization of the Union army following the First Battle of Bull Run. Electing to stay with the 2nd Wisconsin Infantry, Fairchild was soon commissioned lieutenant colonel and, with his regiment now a part of the famed Iron Brigade within the Army of the Potomac, participated in the Second Battle of Bull Run. One week thereafter, on September 8, 1862, he was promoted to the rank of colonel of the 2nd Wisconsin Infantry. On February 27, 1863, the Iron Brigade, now under the command of Brig. Gen. Solomon Meredith, was re-designated the "1st Brigade, 1st Division, I Corps", which gave Fairchild the distinction of being the ranking officer among all commissioned officers within the I Corps of the Army of the Potomac during the Spring and Summer of 1863.