Klotz as a surname (German for block) can refer to:

• Klotz (violin makers), a family of German violin makers (also spelt Kloz and Cloz)

• Adolf Klotz, Croatian linguist and writer
• August Klett (Pseudonym: August Klotz), German artist
• Christian Adolph Klotz (1738–1771), German philosopher and writer
• Christopher Klotz (born 1984), American soccer player
• Clemens Klotz (1886–1969), German architect
• Clyde Klotz (born 1961), art director
• Florence Klotz (1920–2006), costume designer
• Frank Klotz (born 1950), U.S. Air Force general
• Hans Klotz (1900–1987), German organist and musicologist
• Ignatius Klotz (1843–1911), American farmer and politician
• Jeff S. Klotz (born 1990), German Author, publisher, museum director and entrepreneur
• Józef Klotz (1900–1941), Polish footballer
• Karlheinz Klotz (born 1950), German sprinter
• Louis Klotz, Basketball player, nicknamed "Red"
• Louis-Lucien Klotz (1868–1930), French politician
• Martin Klotz (fl. 1800), Austrian mountaineer
• Mathias Klotz (born 1965), Chilean architect
• Matthew Klotz (born 1996), American male deaf swimmer and reality television contestant.
• Nicolas Klotz (born 1954), French film director
• Otto Julius Klotz (1852–1923), Canadian astronomer and Dominion Surveyor
• Reinhold Klotz (1807–1870), German classical scholar
• Robert Klotz (1819–1895), American politician
• Sebastian Klotz (1696–1775), violin maker
• Sibyll-Anka Klotz (born 1961), German politician
• Suzanne Klotz (born 1944), artist
• Ulrike Klotz (born 1970), German gymnast

• Hans Klot, from the French television series Code Lyoko
• Roger Klotz, from the American television series Doug

• Cloots