Oster is a surname. Notable people with the surname include:
- Daniel Oster (1938–1999), French writer
- Emily Oster (born c. 1980), American economist and academic, daughter of Sharon
- Ernst Oster (1908—1977), German pianist, musicologist and music theorist
- George Oster (1940–2018), American mathematical biologist
- Grigoriy Oster (born 1947), Russian children's book author and scriptwriter
- Hans Oster (1887–1945), German World War II general, and anti-Nazi resistance figure
- Harry Oster (1923–2001), American folklorist and musicologist
- Heinrich Oster (1878–1954), German chemist, businessman and Nazi war criminal
- Jack Oster (c. 1910–?), British rugby player
- Jeffrey W. Oster, US Marine Corps lieutenant general
- Jennifer Oster (born 1986), German footballer
- John Oster (born 1978), British football player
- Josef Oster (born 1971), German politician
- Shai Oster, American journalist
- Sharon Oster (1948–2022), American economist and academic
- Stefan Oster (born 1965), German Catholic bishop