Robert or Bob Dietz may refer to:
- Robert H. Dietz (1921–1945), American Medal of Honor recipient
- Robert S. Dietz (1914–1995), American geophysicist and oceanographer
- Robert Edwin Dietz (1818–1897), American businessman
- Bob Dietz (1917–1999), American professional basketball player
- Robert L. Deitz (1950-), American lawyer and intelligence officer