Hassler (also Haßler, Häßler, Hässler, Hasler, ...) is a toponymic surname derived from a number of places called Hasel or Hassel in German-speaking parts of Europe.

Notable people with this name include:

Musicians

• A musical dynasty in Nuremberg
  • Isaak Hassler (c.1530 – 1591), organist and father of three brothers:
    • Kasper Hassler (1562–1618), minor composer and publisher
    • Hans Leo Hassler (1564–1612), an important German composer and organist
    • Jakob Hassler (1569–1622), composer most noted for his keyboard works
• Johann Wilhelm Hässler (1747–1822), German organist and composer

Athletes

• Nicole Hassler (1941–1996), French figure skater
• Des Hasler (b. 1961), Australian rugby league footballer and coach
• Thomas Häßler (b. 1966), former German football player and 1990 World Cup winner
• Dominic Hassler (b. 1981), Austrian football player

Other professions

• Johann Hasler (b. 1548, died after 1602), Swiss theologian and physician
• Ferdinand Rudolph Hassler (1770–1845), first US Coast Survey superintendent
• Friday Hassler (1935–1972), American NASCAR driver
• Hassler Whitney (1907–1989), American mathematician
• Herbert "Blondie" Hasler (1914–1987), British Marines officer and later a noted single-handed sailor
• Rolf Hassler (1914–1984), German neurobiologist
• Eveline Hasler (b. 1933), Swiss writer
• Jon Hassler (1933–2008) American novelist for whom is named the Jon Hassler Theater in Plainview, Minnesota
• Marie Hasler (b. 1948), New Zealand politician
• Harry Hasler, fictional alter ego of Viktor Giacobbo, one of his most popular satirical figures
• Otmar Hasler (b. 1953), Prime Minister of Liechtenstein
• Uwe Hassler(de) (b. 1963), German professor of statistics and econometrics
• Irací Hassler (b. 1990), Chilean politician and economist