Charles III (born 1948) is King of the United Kingdom and 14 other Commonwealth realms.
Charles III may also refer to:
- Charles III of the Carolingian Empire ("Charles the Fat") (839–888)
- Charles III of West Francia ("Charles the Simple") (879–929)
- Charles III of Anjou (1290–1325)
- Charles III of Alençon (1337–1375)
- Charles III of Naples (1345–1386)
- Charles III of Navarre (1361–1425)
- Charles III, Duke of Savoy (1486–1553)
- Charles III, Duke of Bourbon (1490–1527)
- Charles III, Duke of Lorraine (1543–1608)
- Charles III, Prince of Guéméné (1655–1727)
- Charles III Philip, Elector Palatine (1661–1742)
- Charles III William, Margrave of Baden-Durlach (1679–1738)
- Charles III of Hungary (Charles VI, Holy Roman Emperor) (1685–1740)
- Charles III of Spain (1716–1788)
- Charles III John of Norway (Charles XIV John of Sweden and Norway) (1763–1844)
- Charles Albert III, Prince of Hohenlohe-Waldenburg-Schillingsfürst (1776–1843)
- Charles III, Prince of Monaco (1818–1889)
- Charles Egon III, Prince of Fürstenberg (1820–1892)
- Charles III, Duke of Parma (1823–1854)
- Charles III of Bohemia (Charles I of Austria) (1887–1922)