| Ó Néill, Pádraig |
| S-00002332 | ANS - Impact of the Norman Invasion on Irish Literature | ||
| Oaks, Jeffrey A |
| S-00001977 | MPR - Birth Dates of Valentinian II and Valentinian III | ||
| Obreen, H G A |
| S-00002611 | TAN - English Forces in the Netherlands | ||
| S-00002642 | TAN - Notes from the Netherlands | ||
| O'Brien, M A |
| S-00001082 | Corpus Genealogiarum Hiberniae (Volume 1) | ||
| Oggins, Robin S |
| S-00001872 | MPR - Hawkers and Falconers | ||
| S-00001937 | MPR - Richard of Ilchester's Inheritance | ||
| Oggins, Virginia Darrow |
| S-00001872 | MPR - Hawkers and Falconers | ||
| S-00001937 | MPR - Richard of Ilchester's Inheritance | ||
| O'Keeffe, Tadhg |
| S-00002530 | ANS - Ballyloughan, Ballymoon and Clonmore | ||
| Oliva, A M |
| S-00000017 | Genealogie Medioevali di Sardegna | ||
| Oliva, Marilyn |
| S-00001962 | MPR - Late Medieval English Nuns | ||
| S-00002023 | MPR - Monastic and Clerical Careers among Family Members | ||
| Oliver, Arthur Maule, OBE |
| S-00002657 | AAC - Baronies of Bolbec | ||
| Olson, Sherri |
| S-00001946 | MPR - Family Linkages and the Structure of the Local Elite | ||
| Ormerod, George |
| S-00001602 | TPG - Connexion of Arderne of Cheshire | ||
| Ormiston, (Lt-Col) T L (1922-1954) |
| S-00000210 | GMG - Early Scottish Mormaerships (Letter from Lt-Col TL Ormiston) | ||
| Orpen, Goddard Henry, LittD |
| S-00000059 | EHR - Calendar of Gormanston Register (Review) | ||
| S-00000078 | GMG - Origin of the Fitzmaurices | ||
| S-00001230 | Ireland under the Normans, 1169-1216 | ||
| S-00001231 | Ireland under the Normans, 1216-1333 | ||
| Otárola, Alfredo J |
| S-00000602 | Datos y Linajes | ||
| Owen, Dorothy M |
| S-00001558 | ANS - Bishop's Lynn | ||
| S-00002086 | ANS - Norman Cathedral at Lincoln | ||
| Owen, Edward, MA |
| S-00002658 | AAS - Decline of the Tudors of Penmynydd | ||
| D'Oyly Bayley, W |
| S-00001682 | TPG - Ancient Deeds, Bucks and Oxon | ||
| S-00001613 | TPG - Babington and D'Oyly | ||
| S-00001663 | TPG - Family of Hodilow | ||
| S-00001618 | TPG - Manor of Hutton Bonville in Birkby Parish | ||
| S-00001610 | TPG - Pedigree of the Early D'Oylys | ||
| S-00001665 | TPG - Pedigree of the Tregoze Family | ||