18th century inventor James Watt was a Scottish instrument maker whose improvements on the steam engine helped advance the Industrial Revolution. After an apprenticeship in England, Watt returned to Scotland in 1756 and began earning jobs from professors at the University of Glasgow. During the 1760s he devoted most of his time to improving the efficiency of steam engines, the mechanical pumps that had been the work of Thomas Savery and Thomas Newcomen a half-century before. The result was a machine that by 1790 had become so popular that Watt is sometimes now mischaracterized as the inventor of the steam engine. He joined Matthew Boulton in business and began selling the Watt steam engine in 1774. Watt's many mechanical advances earned him several patents, and his engines were used for coal mining, textile manufacturing, transportation and a host of other industrial uses. He retired in 1800, a prosperous and venerated inventor, although it is sometimes pointed out that Watt's stubborn protection of his patents probably slowed other technological advances for many years.

Watt is also remembered for measuring the power of his steam engine: his test with a strong horse resulted in his determination that a "horsepower" was 550 foot-pounds per second. The unit of power in the metric system is called the watt; one horsepower equals 746 watts.