John de Witt may refer to:
- Johan de Witt (1625–1672), a Dutch politician who was assassinated
- John DeWitt (psuedonym), an unknown eighteenth century American author of several essays critical of the new Constitution during the debate on its adoption
- John L. DeWitt (1880–1962), U.S. general in World War II who infamously helped initiate the Japanese-American internment
- John DeWitt (athlete) (1881–1930), an American athlete who competed mainly in the hammer throw and won a silver medal