| O. Festival for Opera.Music.Theatre | Rotterdam, Netherlands | FestivalView profile |
| Offenbach Festival | Bad Ems, Germany | FestivalView profile |
| Ojai Music Festival | United States | FestivalView profile |
| Olib Summer Festival | Croatia | FestivalView profile |
| ONE Festival | Omaha, United States | FestivalView profile |
| Open-Air Festival Szeged | Szeged, Hungary | FestivalView profile |
| Oper im Berg Festival | Salzburg, Austria | FestivalView profile |
| Oper im Steinbruch | Eisenstadt, Austria | FestivalView profile |
| Oper Klosterneuburg | Klosterneuburg, Austria | FestivalView profile |
| Oper Maxlrain | Salzburg, Austria | FestivalView profile |
| Oper Oder-Spree | Beeskow, Germany | FestivalView profile |
| Oper Schenkenberg | Zurich, Switzerland | FestivalView profile |
| Oper Schloss Hallwyl | Seengen, Switzerland | FestivalView profile |
| Opera al Laghetto | Venafro, Italy | FestivalView profile |
| Opera at Jimbour | Fortitude Valley, Australia | FestivalView profile |
| Opera at the Summer Theatre | Varna, Bulgaria | FestivalView profile |
| Opera Barga | Lucca, Italy | FestivalView profile |
| Opera en la Calle | Tijuana, Mexico | FestivalView profile |
| Opera Festival | Daegu, South Korea | FestivalView profile |
| Opera Festival Buenos Aires | Buenos Aires, Argentina | FestivalView profile |
