James Watt (1736–1819) was a Scottish engineer and inventor of a revolutionary new steam engine.
James or Jim Watt may also refer to:
- James Watt junior (1769–1848), Scottish engineer, businessman and activist
- James Cromar Watt (1862–1940), Scottish artist, architect and jeweller
- Jim Watt (rugby union) (1914–1988), New Zealand rugby union player and paediatrician
- James Russell Watt (1935–2022), New Zealand rugby union player
- Sir James Watt (Royal Navy officer) (1914–2009), British surgeon, Medical Director-General of the Royal Navy
- James G. Watt (1938–2023), former US Secretary of the Interior (1981–83)
- Jim Watt (boxer) (born 1948), Scottish boxer
- Jim Watt (ice hockey) (born 1950), American ice hockey player
- James Watt (diplomat) (born 1951), British ambassador
- James Watt (loyalist) (born 1952), former Northern Irish loyalist paramilitary
- HMS James Watt (launched 1853), steam- and sail-powered Royal Navy ship named after the inventor
- James Watt College (founded 1908), Greenock, Scotland
- James Watt (actuary) (1863–1945), Scottish actuary and geographer
- James Watt (brewery owner), owner of BrewDog pub chain