Leopold III may refer to:
Leopold III, Margrave of Austria (1073–1136), sixth Margrave of Austria Leopold III, Duke of Austria (1351–1386), co-Archduke of Austria and co-Duke of Styria Leopold III, Duke of Anhalt-Dessau (1740–1817), first Duke of Anhalt-Dessau Leopold III, Prince of Lippe (1821–1875) Leopold III of Belgium (1901–1983), fourth King of the Belgians