| O'Brien, Richard (1) | O'Brien, Dan (1) | O'Brien, John (8) |
| O'Carroll, Dean (2) | O'Casey, Sean (3) | O'Connell, Richard (1) |
| O'Connor, Eva (1) | O'Connor, John (2) | O'Donnell, Mark (1) |
| O'Donnell, Dean (1) | O'Donnell, Ronan (4) | O'Donovan, John (1) |
| O'Dwyer, Eamonn (3) | O'Flaherty, Michael (1) | O'Hara, John (1) |
| O'Hare, Jeanie (1) | O'Keefe, Laurence (3) | O'Mahony, John Sean (1) |
| O'Malley, Mike (2) | O'Malley, Mary (1) | O'Neill, Rosary Hartel (10) |
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| O'Rowe, Mark (10) | O'Thomas, Mark (3) | O'Toole, Maureen A. (1) |
| O'Toole, Austin (1) | Oates, Joyce Carol (1) | Oberacker, Richard (2) |
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| Okita, Dwight (1) | Oklahoma, D. K. (1) | Okoh, Janice (2) |