Barnhart is a surname. Notable people with the surname include:
- Berta Barnhart, member of Seattle City Planning Commission
- Brian Barnhart, American auto racing executive
- Clarence Barnhart (1900–1993), American lexicographer
- Clyde Barnhart (1895–1980), American baseball player
- Dan Barnhart (1912–1965), American football player
- David Barnhart (born 1941), American lexicographer
- Ed Barnhart (born 1968), American archaeologist and explorer
- Edgar Barnhart (1904–1984), American baseball pitcher
- Gordon Barnhart (born 1945), Canadian politician
- Henry A. Barnhart (1858–1934), American politician
- Jeffrey L. Barnhart (born 1956), American politician
- Jennifer Barnhart (born 1972), American puppeteer and actress
- Jo Anne B. Barnhart (born 1950), American civil servant
- John Hendley Barnhart (1871–1949), American botanist and author
- Karsen Barnhart (born 2001), American football player
- Katie Barnhart, American figure skater
- Keith Barnhart (born 1962), American musician
- Les Barnhart (1905–1971), American baseball player
- Martha Barnhart, American civic leader
- Mitch Barnhart (born 1959), American athletic director
- Nicole Barnhart (born 1981), American soccer goalkeeper
- Peter Barnhart, Canadian settler
- Phil Barnhart (born 1946), American politician
- Phyllis Barnhart (1922–2008), American animator and cel painter
- Ray Barnhart (1928–2013), American politician
- Robert Barnhart (1933–2007), American lexicographer
- Tony Barnhart (born 1953), American reporter
- Tucker Barnhart (born 1991), American baseball player
- Vic Barnhart (1922–2017), American baseball player
Cynthia Barnhart (born 1959) is an American civil engineer and academic who has been serving as provost of the Massachusetts Institute of Technology since March 2022. She previously served as the Institute's chancellor from 2014 to 2021.
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