James Watt (wɒt; 30 January 1736 (19 January 1736 OS) – 25 August 1819) was a Scottish inventor, mechanical engineer, and chemist who improved on Thomas Newcomen's 1712 Newcomen steam engine with his Watt steam engine in 1776, which was 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 became interested in the technology of steam engines. He realised that contemporary engine designs wasted a great deal of energy by repeatedly cooling and reheating the cylinder. Watt introduced a design enhancement, the separate condenser, which avoided this waste of energy and radically improved the power, efficiency, and cost-effectiveness of steam engines. Eventually, he adapted his engine to produce rotary motion, greatly broadening its use beyond pumping water.
Watt attempted to commercialise his invention, but experienced great financial difficulties until he entered a partnership with Matthew Boulton in 1775. The new firm of Boulton and Watt was eventually highly successful and Watt became a wealthy man. In his retirement, Watt continued to develop new inventions though none was as significant as his steam engine work.
As Watt developed the concept of horsepower, the SI unit of power, the watt, was named after him.
James Watt was born on 19 January 1736 in Greenock, Renfrewshire, the eldest of the five surviving children of Agnes Muirhead (1703–1755) and James Watt (1698–1782). His mother came from a distinguished family, was well educated and said to be of forceful character, while his father was a shipwright, ship owner and contractor, and served as the Greenock's chief baillie in 1751. The Watt family's wealth came in part from Watt's father's trading in slaves and slave-produced goods.
Watt's parents were Presbyterians and strong Covenanters, but despite his religious upbringing he later became a deist. Watt's grandfather, Thomas Watt (1642–1734), was a teacher of mathematics, surveying and navigation and baillie to the Baron of Cartsburn.