Butterfield Overland Mail was a stagecoach service in the United States operating from 1858 to 1861. It carried passengers and U.S. Mail from two eastern termini, Memphis, Tennessee, and St. Louis, Missouri, to San Francisco, California. The routes from each eastern terminus met at Fort Smith, Arkansas, and then continued through Indian Territory (Oklahoma), Texas, New Mexico, Arizona, Mexico, and California ending in San Francisco. On March 3, 1857, Congress authorized the U.S. postmaster general, at that time Aaron V. Brown, to contract for delivery of the U.S. mail from St. Louis to San Francisco. Prior to this, U.S. Mail bound for the Far West had been delivered by the San Antonio and San Diego Mail Line since June 1857.

A stagecoach is a four-wheeled public transport coach used to carry paying passengers and light packages on journeys long enough to need a change of horses. It is strongly sprung and generally drawn by four horses although some versions are drawn by six horses.