John Keegan (1934–2012) was a British military historian.
John Keegan may also refer to:
- John Keegan (footballer) (born 1981), English professional footballer
- John Keegan (politician) (1867–1941), Australian trade unionist and politician
- John Keegan (writer), Irish mythologist
- John C. Keegan (born 1952), Retired American judge and politician from Arizona