Harnett may refer to:
- Cornelius Harnett (1723–1781), American statesman
- Curt Harnett (born 1965), Canadian racing cyclist
- Cynthia Harnett (1893-1981), English writer of children's historical fiction.
- Ricci Harnett, British actor
- William Harnett (1848–1892), Irish-American painter