Just is a surname. Notable people with the surname include:
- Alexander Just (1874–1937), German/Hungarian chemist and inventor
- Carl Just (1897–1990), Norwegian journalist
- Cassià Maria Just (1926–2008), Catalan abbot
- Ernest Everett Just (1883–1941), American biologist
- Florian Just (born 1982), German pairs skater
- Gustav Just (1921–2011), East German writer and editor
- Jesper Just (born 1974), Danish artist
- Joe Just (1916–2003), American baseball player
- Johann August Just (c.1750–1791), German composer active in the Netherlands
- John Just (1797–1852), English archaeologist and botanist
- John Augustus Just (1854–1908), German-born American chemist and inventor
- Karsten Just (born 1968), East German sprinter
- Klaus Just (born 1964), West German sprinter
- Marcel Just, American psychologist and cognitive neuroscientist
- Myron Just (born 1941), American politician and farmer from North Dakota
- Paul Just (born 1964), German-born Canadian pole vaulter
- Theodore Just (1886–1937), British athlete
- Ward Just (born 1935), American writer