De Witt is a surname of Dutch origin meaning "the white". In America, the name is usually concatenated to DeWitt. Notable people with the surname include:
- Alexander De Witt (1798–1879), American politician
- Conrad de Witt [fr; nl] (1824–1909), French politician
- Cornélis Henri de Witt [fr; nl] (1828–1889), French politician
- David M. De Witt (1837–1912), American politician
- Elmo De Witt (died 2011), South African filmmaker
- Francis B. De Witt (1849–1929), American politician
- Henriette Guizot de Witt (1829–1908), French writer
- Jacob De Witt (1785–1859), Canadian politician
- Jacob H. De Witt (1784–1867), American politician
- Marguerite de Witt (1853–1924), French activist, daughter of Conrad and Henriette
- Pauline de Witt (1831–1874), French historian
- Simeon De Witt (1756–1834), American cartographer