The Spencer repeating rifles and carbines were early American lever-action firearms invented by Christopher Spencer. The Spencer was the world's first military metallic-cartridge repeating rifle, and over 200,000 examples were manufactured in the United States by the Spencer Repeating Rifle Co. and Burnside Rifle Co. between 1860 and 1869. The Spencer repeating rifle was adopted by the Union Army, especially by the cavalry, during the American Civil War but did not replace the standard issue muzzle-loading rifled muskets in use at the time. Among the early users was George Armstrong Custer. The Spencer carbine was a shorter and lighter version designed for the cavalry.

The carbine .54 calibur version was very popular with the cavalry of both the Union and Confederate armies and was issued in much larger numbers than other carbines of the war and was top in production in front of the Spencer or Burnside carbine. The falling-block action lent itself to conversion to the new metallic cartridges developed in the late 1860s, and many of these converted carbines in .50-70 Government were used during the Indian Wars in the decades immediately following the Civil War.[7]