| Team | Nickname | Intl | Type | Ground |
|---|---|---|---|---|
| Zmaji (the Dragons) Zeleno-beli (Green-Whites) | Men | No Ground | ||
| Olimpik Donetsk | Men | Tolka Park | ||
| Olimpiyets Nizhny Novgorod | Men | Unknown | ||
| Oliver Bond Celtic | Men | Unknown | ||
| St. Oliver Plunkett | Men | Unknown | ||
| Olympia | Men | Unknown | ||
| Olympiacos | Men | Unknown | ||
| Olympic Charleroi | Men | Unknown | ||
| Olympique du Kef | Men | Unknown | ||
| Lyonnais | Men | Parc Olympique Lyonnais | ||
| OSQ | Men | Unknown | ||
| The Town | Men | St Julian's Road | ||
| Oman | ✅ | Men | Unknown | |
| Omonia Nicosia | Men | Unknown | ||
| Once Caldas | Men | Unknown | ||
| Onduparaka | Men | Unknown | ||
| Orange County | Men | Unknown | ||
| Salesians | Men | Gozo Stadium | ||
| Ordabasy | Men | Unknown | ||
| Orduspor | Men | Unknown | ||
| Orebro | Men | Tolka Park | ||
| Orenburg | Men | Unknown | ||
| Orgryte | Men | Unknown | ||
| Orlando City | Men | Unknown | ||
| Orlando Pride | Women | Unknown | ||
| Osijek W | Women | Unknown | ||
| Osmanispor | Men | Unknown | ||
| Oss | Men | Unknown | ||
| Men | Ingfield Stadium | |||
| Ostersund | Men | Tolka Park | ||
| The Fury | Men | TD Place Stadium | ||
| Den Dreel | Men | Unknown | ||
| The Hoops | Men | Unknown | ||
| The U's | Men | Kassam Stadium | ||
| Oxford United Stars | Men | Unknown | ||
| Pachuca | Men | Unknown | ||
| Os Castores | Men | Unknown | ||
| Men | Ruby Civil Arena | |||
| PAEEK | Men | Keryneia Epistrophi | ||
| Pafos | Men | Unknown | ||
| Men | Nyetimber Lane | |||
| Men | Unknown | |||
| Paxtakorlar | Men | Unknown | ||
| Men | Unknown | |||
| Verdao | Men | Unknown | ||
| Panama | ✅ | Men | Unknown | |
| Panama | ✅ | Women | Unknown | |
| Panathinaikos | Men | Tolka Park | ||
| Panavezys | Men | Unknown | ||
| Kanarinia | Men | Unknown |
