| Registered Name | Owner / Club | Status |
|---|---|---|
| Oakport Ringo Star | Laura Mullooly Glenway | Approved |
| Oakvale Captain | Pat Ronayne Coolbell | Approved |
| Oasis Spirit | Grainne Murphy Unicorn | Approved |
| Oates | Patricia Newman Mosstown | Approved |
| Oatfields Maggie May | Sinead White Clonlara | Approved |
| OB Ricardos Polly | Sarah Malone Kilronan | Approved |
| Oban Van De Suydersee | Tara Phelan Warrington | Approved |
| Oberon's Dream (IRE) | Michelle Brannigan Moyglare | Approved |
| Observation (GB) | Miriam Kelly Waterford | Approved |
| Obvious Flair | Aishling Kelly Ballinasloe | Approved |
| Ocala Hobeau | Shauna Clarke Ashbrook | Approved |
| Ocean Murray | Cliona O' Connell Earl's Well | Approved |
| Ochilmore Boy | Ciaran Curran Calliaghstown | Approved |
| ODT Silky Seal | Gary Cotter Earl's Well | Approved |
| Ogie | Caitlin Steel South West | Approved |