| Name | Total | Name | Total |
|---|---|---|---|
| O’Neil | 2 | Orange, of | 1 |
| O’Neil, O'Neil | 1 | Oranje Nassau, van | 5 |
| Oades | 1 | Orbais, d' | 1 |
| Oakeley | 1 | Orbin | 1 |
| Oakes | 1 | Orchard | 2 |
| Oakley | 1 | Ord | 3 |
| Oakman | 1 | Orde | 3 |
| Ober | 1 | Ordway | 1 |
| Oberpriller | 2 | Oriatto | 1 |
| Ochitwa | 4 | Orkney, of | 2 |
| ode Rumigny | 1 | Orléans-Longueville, d' | 3 |
| Odegard | 9 | Orleans, d' | 26 |
| Odingsells | 1 | Ormsby-Gore | 1 |
| Oelke | 1 | Orr | 2 |
| Oettingen-Spielberg | 1 | Ortiz | 2 |
| Offen | 6 | Orton | 1 |
| Ogden | 3 | Osborn | 1 |
| Ogilvie-Grant | 1 | Osborne | 6 |
| Ogle | 1 | Ost | 1 |
| Ogley | 3 | Osterhoudt | 1 |
| Oilly, de | 1 | Oswald | 1 |
| Okeover | 1 | Oswin | 1 |
| Okeston | 1 | Othick | 2 |
| Old | 2 | Otter | 9 |
| Old, Old | 1 | Oudlap | 2 |
| Oldcorn | 2 | Oughton | 2 |
| Oldenburg | 2 | Outhwaite | 2 |
| Oldfield | 3 | Overfield | 1 |
| Oldham | 1 | Overton | 3 |
| Oldroyd | 1 | Overton, Gray | 1 |
| Oliphant | 2 | Overy | 1 |
| Oliver | 9 | Owen | 8 |
| Olsen, Olson | 1 | Owens | 5 |
| Olson | 13 | Owston | 1 |
| Olson, Olson | 2 | Oxburgh | 1 |
| Olsson | 1 | Oxby | 1 |
| Oltrogge | 4 | Oxenford | 6 |
| Olwell | 1 | Oxford | 1 |
| Omer, St. | 3 | Oxley | 4 |
| ONeil | 1 | Oxtaby | 1 |
| Onn | 1 | Oxtoby | 8 |
| OOSTENRIJK, van | 1 | Oyston | 1 |
| Oppenheimer | 1 | - | - |