The Whitehead torpedo was the first self-propelled or "locomotive" torpedo ever developed. It was perfected in 1866 by British engineer Robert Whitehead from a rough design conceived by Giovanni Luppis of the Austro-Hungarian Navy in Fiume. It was driven by a three-cylinder compressed-air engine invented, designed, and made by Peter Brotherhood. Many naval services procured the Whitehead torpedo during the 1870s, including the US Navy. This early torpedo proved itself in combat during the Russo-Turkish War when, on 16 January 1878, the Ottoman ship Intibah was sunk by Russian torpedo boats carrying Whiteheads, though this story has been disputed in one book.

A modern torpedo is an underwater ranged weapon launched above or below the water surface, self-propelled towards a target, and with an explosive warhead designed to detonate either on contact with or in proximity to the target. Historically, such a device was called an automotive, automobile, locomotive, or fish torpedo; colloquially a fish. The term torpedo originally applied to a variety of devices, most of which would today be called mines. From about 1900, torpedo has been used strictly to designate a self-propelled underwater explosive device.