- Obulco (ancient place), Hispania Ulterior2 objects
- Odessus, ancient Thrace2 objects
- Oilaunes (ancient place)1 objects
- Oreus (ancient place)1 objects
- Orippo (ancient place), Hispania Ulterior1 objects
- Orvieto, Umbria, Central Italy1 objects
- Osca (ancient place)1 objects
- Oschersleben, Saxony-Anhalt, Germany8 objects
- Ostseebad Arendsee, Mecklenburg-Vorpommern, Germany3 objects
- Ostseebad Graal-Müritz, Mecklenburg-Vorpommern, Germany3 objects
- Ottensheim, Upper Austria4 objects