Jan III may refer to:
Jan III van Diest (died 1340) Jan III of Oświęcim (1366–1405) Jan III van Montfoort (c. 1448 – 1522) John III, Lord of Bergen op Zoom (1452–1532) John III Sobieski (1629–1696) Jan III Sobieski High School in Kraków Jan III Sobieski (cigarette)