James Watt, FRS, FRSE (19 January 1736 – 25 August 1819) is a Scottish inventor and mechanical engineer whose improvements to the Newcomen steam engine are fundamental to the changes brought by the Industrial Revolution in both his native Great Britain and the rest of the world.

While working as an instrument maker at the University of Glasgow, Watt becomes interested in the technology of steam engines.

He realizes that contemporary engine designs waste a great deal of energy by repeatedly cooling and reheating the cylinder.

Watt introduces a design enhancement, the separate condenser, which avoids this waste of energy and radically improves the power, efficiency, and cost-effectiveness of steam engines.

Eventually he adapts his engine to produce rotary motion, greatly broadening its use beyond pumping water.

Watt attempts to commercialize his invention, but experiences great financial difficulties until he enters a partnership with Matthew Boulton in 1775.

The new firm of Boulton and Watt is eventually highly successful and Watt becomes a wealthy man.

In his retirement, Watt continues to develop new inventions though none are as significant as his steam engine work.

He dies in 1819 at the age of 83.

Watt has been described as one of the most influential figures in human history.

He develops the concept of horsepower and the SI unit of power, the watt, is named after him.