A mechanical traveller is a moving part of a machine, typically a ring that slides between different positions on a supporting rod when the machine goes through its operating cycle.

The 1815 Philadelphia train accident occurred on 31 July 1815, in Philadelphia, County Durham, England, when an early experimental railway locomotive, Brunton's Mechanical Traveller, suffered a boiler explosion.

William Chapman at the Butterley Company in 1812, attempted to use a steam engine which hauled itself along a cable, while, at the same company, Brunton had produced the even less successful "mechanical traveller", or Steam Horse.