Messmer is a surname. Notable people with the surname include:

• Henry Messmer (1866–1899), Swiss-American architect
• Ivan Messmer (1931–2015), Canadian politician
• John Messmer (1884–1971), American athlete
• Léon Messmer (1900–1987), French Roman Catholic bishop in Madagascar
• Magali Messmer, Swiss triathlete
• Mark Messmer, American politician
• Mindi Messmer, American politician
• Nikolaus Messmer (1954–2016), Russian Roman Catholic bishop, Apostolic administrator or Kyrgyzstan
• Otto Messmer (1892–1983), American animator
• Otto Messmer (Jesuit) (1961–2008), Russian Jesuit priest, head of Jesuits in the CIS
• Pearl Ray Messmer (1892–?), Australian orchidologist
• Pierre Messmer (1916–2007), French Prime Minister
• Sebastian Gebhard Messmer (1847–1930), Swiss-born Roman Catholic archbishop of Milwaukee
• Wayne Messmer, announcer for the Chicago Cubs
• Messmer (hypnotist), stage name of Éric Normandin, French Canadian hypnotist