John Llewellyn
John Llewellyn may refer to:
- John Llewellyn (fencer), British fencer who appeared at three Olympic Games
- John Llewellyn (racing driver), British former auto racing driver
- Sir John Llewellyn (academic), academic administrator in New Zealand and Great Britain
- John Anthony Llewellyn, British-born American scientist and NASA astronaut
- Sir John Dillwyn-Llewellyn, 1st Baronet, Welsh Conservative Member of Parliament
- John Seys-Llewellyn, Welsh barrister and judge
- John Llewellin, 1st Baron Llewellin, British army officer and politician