Alexander III may refer to:
- Alexander III of Macedon (356 BC – 323 BC), also known as Alexander the Great
- Alexander (Byzantine emperor) (870–913), Byzantine emperor
- Pope Alexander III (1100s–1181)
- Template:Ill, grand duke of Vladimir (1328–1331), prince of Suzdal
- Alexander III of Scotland (1241–1286), king of Scotland
- Alexander III of Imereti (1609–1660), king of Imereti
- Alexander III of Russia (1845–1894), emperor of Russia
- {{#invoke:Lang|lang}}, an arch bridge that spans the Seine in Paris
- Russian battleship {{#invoke:Lang|lang}}, Russian warship
- Alexander III of Antioch (1869–1958), Greek Orthodox patriarch of Antioch