John Hewitt may refer to:
- John Hewitt (priest) (died 1588), English Roman Catholic priest and Catholic martyr, beatified in 1929
- John Hewitt (antiquary) (1807–1878), English official
- John Hill Hewitt (1801–1890), newspaper editor
- John Napoleon Brinton Hewitt (1859–1937), linguist
- John Hewitt (herpetologist) (1880–1961), South African zoologist and archaeologist
- John Haskell Hewitt (1835–1920), American classical scholar and educator
- John Hewitt (poet) (1907–1987), poet from Northern Ireland
- John Hewitt (mayor) (1943–2011), New Zealand local-body politician
- John Hewitt (entrepreneur) (born 1949), U.S. entrepreneur
- John Hewitt (footballer) (born 1963), Scottish former footballer and manager
- John Hewitt (pentathlete) (born 1925), British Olympic pentathlete
- John Hewitt, author of the Ringworld role-playing game
- John K. Hewitt (born 1952), behavioral geneticist from Hampshire, England
- John Marshall Hewitt (1841–1888), member of the Arkansas House of Representatives
- John Hewitt (rugby union) (born 1960), Irish rugby union player