| Name | # Entries |
|---|---|
| O'brien | 845 |
| O'connor | 798 |
| Oliver | 729 |
| O'neill | 618 |
| Osborne | 553 |
| Olsen | 494 |
| Owen | 445 |
| O'sullivan | 411 |
| O'connell | 393 |
| O'donnell | 379 |
| Orr | 295 |
| O'leary | 249 |
| Owens | 165 |
| Ormsby | 160 |
| O'reilly | 149 |
| O'malley | 141 |
| O'callaghan | 132 |
| Ogle | 116 |
| Oakley | 109 |
| O'hara | 106 |
| Oldham | 98 |
| Olliver | 94 |
| O'neil | 86 |
| O'donoghue | 82 |
| O'shea | 81 |
| Otago | 81 |
| Osborn | 79 |
| O'loughlin | 79 |
| Olson | 75 |
| O'keeffe | 74 |
| O'dea | 72 |
| O'kane | 69 |
| O'hagan | 68 |
| Ocean | 68 |
| O'halloran | 68 |
| Ormond | 67 |
| O'keefe | 67 |
| Oates | 66 |
| O'regan | 66 |
| O'grady | 64 |
| Orange | 64 |
| Overton | 60 |
| Ogden | 57 |
| Ong | 56 |
| Otto | 55 |
| Oram | 49 |
| Opus | 47 |
| O'carroll | 46 |
| One | 43 |
| Oxford | 42 |
| Oxenham | 40 |
| Oasis | 40 |
| Overend | 39 |
| O'shaughnessy | 39 |
| Otaki | 36 |
| O'flaherty | 35 |
| Oswald | 35 |
| Ormandy | 33 |
| O'toole | 33 |
| Overland | 33 |
| Oxley | 33 |
| O'driscoll | 32 |
| Orton | 32 |
| On | 32 |
| O'dwyer | 31 |
| Ogilvy | 31 |
| Olive | 30 |
| Osman | 29 |
| Ohlson | 28 |
| Ogier | 25 |
| Old | 25 |
| O'byrne | 24 |
| O'gorman | 24 |
| Obrien | 24 |
| Otara | 24 |