John Barclay may refer to:
- John Barclay (poet) (1582–1621), Scottish satirist and Latin poet
- John Barclay (Berean) (1734–1798), Scottish theological writer
- John Barclay (clergyman) (1795–1826), Canadian Church of Scotland clergyman
- John Barclay (cricketer) (born 1954), cricketer
- John Barclay (rugby union) (born 1986), Scottish international rugby union player, playing for Glasgow
- John Barclay (anatomist) (1758–1826), anatomist
- John Barclay, Captain in Danish-Norwegian military, 1643 to 1645, thought to have been the first male member of Clan Barclay
- John Barclay (mayor) (1749–1824), American soldier, politician, and jurist; mayor of Philadelphia in 1791
- John Barclay, survivor of the shipwreck of HMS Birkenhead in 1852
- John Barclay (marine) (1741–1823), British Royal Marines general