British engineer and inventor.
Born in Greenock, Scotland, Watt set up business in Glasgow in 1757 as mathematical instrument maker to the University. In 1763/64, while repairing a Newcomen engine brought to his workshop, he found that he could improve the efficiency of the engine by using a separate steam condenser. In 1774 he went into partnership with Matthew Boulton (1728-1809) and began manufacture of the new engine in Birmingham.
Watt died on 25 August 1819. The SI unit of power is named after him.