Klotz is a surname (German for block), can refer to:
- Klotz (violin makers), a family of German violin makers (also spelt Kloz and Cloz).
- the last name of the following people:
- Adolf Klotz, Croatian linguist and writer
- August Klett (Pseudonym: August Klotz), German artist
- Christian Adolf Klotz (1738-1771), German philosopher and writer.
- Christopher Klotz, American soccer player.
- Clemens Klotz, German architect.
- Clyde Klotz, art director.
- Florence Klotz, costume designer.
- Frank Klotz, US Air Force general
- Henry W. Klotz, Sr., American service station proprietor.
- Karlheinz Klotz, German sprinter.
- Louis Klotz, Basketball player nicknamed "Red".
- Louis-Lucien Klotz, French politician.
- Martin Klotz, Austrian mountaineer.
- Mathias Klotz, Chilean architect.
- Nicolas Klotz, French film director.
- Otto Julius Klotz, Canadian astronomer and Dominion Surveyor.
- Reinhold Klotz, German classical scholar.
- Robert Klotz (1819-1895), American politician.
- Sebastian Klotz (1696–1768), violin maker.
- Ulrike Klotz, German gymnast.
- the last name of the following fictional characters:
- Hans Klotz, from the French television series Code Lyoko
- Roger Klotz, from the American television series Doug.