XXIII Corps was a corps of the Union Army during the American Civil War. It served in the Western Theater as part of the Army of the Ohio. The corps was organized in April 1863 by order of the departmental commander, Ambrose E. Burnside. Along with Burnside's old IX Corps, which had been sent west with him after Fredericksburg, it was to maintain a primarily defensive position in Eastern Tennessee and Kentucky. It originally consisted of two divisions under the overall command of General George L. Hartsuff.