Kagan is a primarily Russian-Jewish surname which is derived from the surname Cohen (in Russian the consonant h is replaced with the consonant g).
Notable people with the Kagan surname include:
- Bernhard Kagan (1866–1932), German chess player, writer, publisher, editor, and organizer
- Carolyn Kagan, British psychologist
- Daryn Kagan (born 1963), former American newscaster
- David Kagan (born 1949), American bishop
- Donald Kagan (1932–2021), Yale historian specializing in ancient Greece (Frederick and Robert Kagan's father)
- Elena Kagan (born 1960), Associate Justice of the U.S. Supreme Court, dean of Harvard Law School, and U.S. Solicitor General (under President Obama).
- Emily Kagan (born 1981), American mixed martial artist
- Frederick Kagan (born 1970), professor of military history (Robert Kagan's brother)
- Henri Kagan, French chemist
- Helena Kagan (1889-1978), pioneer-pediatrician of Israel
- Janet Kagan (1946–2008), author
- Jeremy Kagan (born 1945), American television director
- Jerome Kagan (1929–2021), children developmental psychology
- Joseph Kagan, Baron Kagan (1915–1995), British industrialist
- Kimberly Kagan (born 1972), military historian (Frederick Kagan's wife)
- Lazar Kaganovich (1893-1991), Soviet politician and administrator
- Mimi Kagan (1918–1999), Russian-born American modern dancer, choreographer
- Oleg Kagan (1946–1990), Russian violinist
- Robert Kagan (born 1958), American historian and political commentator (Frederick Kagan's brother)
- Shelly Kagan, philosopher and ethicist at Yale University
- Shimon Kagan (born 1942), Israeli chess master
- Veniamin Kagan (1869–1953), Russian mathematician
- Vladimir Kagan (1927–2016), German furniture designer
- Yisrael Meir Kagan (1838–1933), Polish-born rabbi, halakhist, and ethicist