Otto is a German, Dutch, Hungarian, Danish, and Swedish surname. Notable people with the surname include:
- Adolph Wilhelm Otto (1786–1845), German anatomist
- Berthold Otto (1859 –1933), German pedagogue
- Catherine Otto, author of echocardiography textbooks
- Christoph Friedrich Otto (1783–1856), German botanist
- Felix Otto (mathematician) (born 1966), German mathematician
- Frei Otto (1925–2015), German architect
- Frank Otto (academic) (1936–2017), American educator and entrepreneur
- Gertrud Otto (1895–1970) German art historian
- Gustav Otto (1883–1926), German aircraft and aircraft-engine designer and manufacturer
- Jan Otto (1841–1916), publisher of Otto's encyclopedia
- John Otto (disambiguation), several people
- Justine Otto (born 1974), German artist
- Lisa Otto (1919–2013), German opera singer
- Mary Otto, American journalist
- Michael Otto (businessman) (born 1943), German businessman
- Nicolaus Otto (1832–1891), coinventor of the Otto cycle
- Rudolf Otto (1869–1937), German theologian
- Shawn Lawrence Otto, American author, filmmaker, political strategist
- Tracy Otto (born 1995), American Paralympic archer
- Venantia Otto (born 1987), Namibian fashion model
- William Tod Otto (1816–1905), American judge
- Walter Friedrich Otto (1874–1958), German philologist