| Oaken Palace Records | 1 August 2012 | — | charitable organization |
| Odd Box Records | April 2009 | Original Production | — |
| Odio Records | 1 January 2018 | Original Production | — |
| Off Me Nut Records | 2010 | Original Production | — |
| Old Gold | — | Reissue Production | — |
| On-U Sound | — | Original Production | 8619 |
| One Little Independent Records | 10 June 2020 | Original Production | 3275 |
| One Little Indian Records | 1985 | Original Production | 3275 |
| Onyx | May 2005 | Imprint | 19017 |
| Opal Records | — | Original Production | — |
| Opal Tapes | 2012 | Original Production | — |
| Opera Rara | 1 January 1970 | — | charitable organization |
| Orbis | 1 June 1970 | Imprint | — |
| Orchid Classics | 2005 | Original Production | — |