Locomotion No. 1 is an early steam locomotive that was built in 1825 by the pioneering railway engineers George and Robert Stephenson at their manufacturing firm, Robert Stephenson and Company. It became the first steam locomotive to haul a passenger-carrying train on a public railway, the Stockton and Darlington Railway (S&DR).

A steam locomotive is a locomotive that provides the force to move itself and other vehicles by means of the expansion of steam. It is fuelled by burning combustible material to heat water in the locomotive's boiler to the point where it becomes gaseous and its volume increases 1,700 times. Functionally, it is a steam engine on wheels.