Demetrius III may refer to:
- Demetrius III of Abkhazia (Template:Floruit), King of Abkhazia
- Demetrius III Aniketos (Template:Floruit), Indo-Greek king
- Demetrius III Eucaerus (died 88 BC), Seleucid king
- Demetrius III of Georgia (Template:Circa–1453), King of Georgia