John Hay (1838–1905) was an American politician; Secretary of State 1898–1905.
John Hay may also refer to:
- John Hay, 1st Lord Hay of Yester (c. 1450–c. 1508)
- John Hay, 2nd Lord Hay of Yester (died 1513), Scottish nobleman
- John Hay (Jesuit) (1546–1608), Jesuit scholar and educator
- John Hay, 1st Earl of Tweeddale (1593–1653), Scottish aristocrat
- John Hay, 1st Marquess of Tweeddale (1625–1697), Lord Chancellor of Scotland
- John Hay, 2nd Marquess of Tweeddale (1645–1713), Scottish nobleman
- John Hay, 4th Marquess of Tweeddale (1695–1762), Scottish nobleman
- John Hay, 12th Earl of Erroll (died 1704), Scottish nobleman
- John Hay of Cromlix (1691–1740), Jacobite noble
- John Hay (moderator) (1566–1627), Scottish minister
- John Hay (academic) (1942–2016), Australian academic
- John Hay (Canadian politician) (1862–1925), Canadian politician
- John Hay (cardiologist) (1873–1959), Liverpool physician
- John Hay (director) (born 1964), English film director
- John Hay (footballer) (fl. 1921–1922), Scottish footballer (Bradford City)
- John Hay (Henley MP) (1919–1998), British Conservative Party politician, Member of Parliament
- John Hay (nature writer) (1915–2011), American author
- John Hay (New South Wales politician) (1816–1892), Australian politician from New South Wales
- John B. Hay (1834–1916), American politician from Illinois
- John H. Hay (1917–1995), U.S. Army general
- John Hay Drummond Hay (1816–1893), British diplomat
- John Le Hay (1854–1926), Irish-born singer and actor
- John MacDougall Hay (1879–1919), Scottish novelist
- John Primrose Hay (1878–1949), British Member of Parliament for Glasgow Cathcart, 1922–1923
- Sir John Hay, 6th Baronet (1788–1838), British baronet and Member of Parliament
- Sir John Hay of Alderston, 1st Baronet (died 1706)
- Sir John Hay of Lands and Barra, "The Incendiary" (1578-1654) Lord Provost of Edinburgh 1637–38
- Sir John Dalrymple-Hay, 3rd Baronet (1821–1912), British admiral and Conservative Member of Parliament
- John Hay (priest) (born 1945), Dean of Raphoe from 2003 to 2013
- SS John Hay, a Liberty ship