| O'Briant | O'Brien | O'Connell | O'Connor | O'Daniel | O'Deas | O'Dell | O'Donnell |
| O'Gorman | O'Hara | O'Haver | O'Keefe | O'Leary | O'Malley | O'Meara | O'Reilly |
| O'Reily | O'Rourke | O'Sullivan | Oak | Oakes | Oas | Oatman | Obender |
| Oberdick | Oberdiear | Oberg | Obert | Obowa | Obradrack | Obright | Odahl |
| Odden | Odeberg | Odegaard | Odegard | Odens | Odland | Odwit | Oechsle |
| Oehler | Oehlman | Oehlmann | Oehlschlager | Oehman | Oelke | Oelrich | Oelschlager |
| Oelslager | Oestreich | Ofenmaher | Offerdahl | Ofstedal | Oftelie | Ogden | Ogle |
| Ogorer | Ogroske | Ogsbury | Ohe | Ohem | Ohlar | Ohlrogge | Ohlson |
| Ohm | Ohman | Ohnsorg | Ohren | Ohsberg | Ohtonen | Oien | Oikari |
| Oiseth | Oja | Ojala | Okerlund | Okerman | Okerstrom | Okesen | Oksness |
| Olafson | Oland | Olander | Olbekson | Oldara | Oldenburg | Oldenettel | Olds |
| Olds-Berg | Olek | Oler | Oles | Olesch | Oleson | Olikain | Olin |
| Oliphant | Oliver | Oliverson | Olli | Ollia | Ollie | Ollikain | Ollila |
| Ollinger | Olmala | Olmstead | Olofson | Olsby | Olsdatter | Olsen | Olsgaard |
| Olson | Olsson | Olstad | Olthoff | Oltman | Olufson | Oman | Omans |
| Omberg | Omley | Ommang | One | Onerheim | Ones | Ongstad | Onken |
| Onskoust | Onstad | Onsum | Oothoudt | Opaker | Opalka | Opatz | Opdahl |
| Ophus | Opmeiler | Opp | Oppegaard | Oppegard | Opsahl | Opsal | Orcutt |
| Ordal | Ordschig | Oren | Orendorff | Orger | Orlando | Ormsby | Ormseth |
| Orndorff | Orpen | Orre | Orrock | Orso | Orstad | Orstrum | Orsund |
| Ortiz | Osahl | Osander | Osborn | Osborne | Oscarson | Oseien | Oseline |
| Osgood | Oshie | Osier | Oskari | Osman | Osmundatter | Osmundsen | Osmundson |
| Ososki | Ost | Ostaberget | Osten | Ostenson | Osteomayer | Osterfeld | Ostermann |
| Ostermeier | Ostgaarden | Ostley | Ostlie | Ostling | Ostlund | Lstradson | Ostrander |
| ostrom | Ostroot | Ostrowski | Ostrum | Ostrus | Oswald | Oszuscik | Otnes |
| Otremla | Ostwald | Ott | Otte | Ottelin | Otterness | Otterson | Ottila |
| Ottman | Otto | Ouart | Oughton | Ouren | Ouse | Ouskouski | Ovenmaa |
| Overacker | Overby | Overgaard | Overland | Overson | Oviest | Ovik | Owen |
| Owens | Oxhovd | Oxley | Oyen | Oyloe | Ozmouski |
| Surnames Found in our Cemetery Records | |||||
| O | |||||