John Hewitt may refer to:

• John Hewitt (pentathlete) (born 1925), British Olympic pentathlete
• John Hewitt (rugby union, born 1928) (1928–2019), Irish rugby union player
• John Hewitt (swimmer) (1941–2017), Welsh swimmer
• John Hewitt (rugby union, born 1960), Irish rugby union player
• John Hewitt (footballer) (born 1963), Scottish footballer and manager

• John Hewitt (priest, died 1588), English Roman Catholic priest and Catholic martyr
• John Hewitt (priest, born 1755) (1755–1804), Anglican priest in Ireland
• John Hill Hewitt (1801–1890), American composer, playwright and poet
• John Hewitt (antiquary) (1807–1878), English antiquarian
• John Haskell Hewitt (1835–1920), American classical scholar and educator
• John Marshall Hewitt (1841–1888), American politician in Arkansas
• J. N. B. Hewitt (John Napoleon Brinton Hewitt, 1859–1937), American linguist and ethnographer
• John Hewitt (herpetologist) (1880–1961), South African zoologist and archaeologist
• John Hewitt (poet) (1907–1987), poet from Northern Ireland
• John Hewitt (mayor) (1943–2011), New Zealand politician
• John Hewitt (entrepreneur) (born 1949), American businessman
• John K. Hewitt (born 1952), British-American behavioral geneticist

• The John and Vivian Hewitt Collection of African-American Art

• Jonathan Hewitt, EastEnders character
• Jack Hewitt (born 1951), American racing driver
• John Hewett (disambiguation)
• John Hewet (disambiguation)