John O'Leary
John O'Leary may refer to:
- John O'Leary (Fenian) (1830–1907), Irish nationalist who was imprisoned in England during the nineteenth century
- John O'Leary (Kerry politician) (born 1933), former Irish Fianna Fáil party politician and TD for Kerry South
- John O'Leary (Wexford politician) (1894–1959), former Irish Labour party politician and TD for Wexford
- John O'Leary (ambassador) (1947 – 2005), former U.S. ambassador to Chile
- John F. O'Leary (1926 – 1987), former U.S. head of Federal Energy Administration
- John O'Leary (journalist), editor of the Times Higher Education Supplement
- John O'Leary (Gaelic footballer)
- John O'Leary (vocalist), lead vocalist for Atlanta band Crazy Anglos
- John O'Leary (blues harmonica artist) , British blues harmonica player, originally with the band Savoy Brown.
- John O'Leary (golfer), Irish Ryder Cup golfer