Lords | Titles by Rank
- Lords of Offreville
- Lords of Ogéviller
- Lords of Ogimont
- Lords of Oiran
- Lords of Oise
- Lords of Oisy
- Lords of Oisy e de Montreuil
- Lords of Olbreuse
- Lords of Oliergues
- Lords of Oliva
- Lords of Oliveira do Bairro
- Lords of Oliveira do Condes
- Lords of Ollioules
- Lords of Olmen
- Lords of Olonde
- Lords of Olonde
- Lords of Omicourt de Fampoux e de Roeux
- Lords of Oñate
- Lords of Onate
- Lords of Ondes
- Lords of Oneglia
- Lords of Ongnies
- Lords of Oordegem
- Lords of Oostmaele
- Lords of Opprebais
- Lords of Oradero
- Lords of Oradour sur Vayres
- Lords of Orbe
- Lords of Orce
- Lords of Orchard
- Lords of Orduña
- Lords of Orgaz
- Lords of Orimont
- Lords of Oriola
- Lords of Orjol
- Lords of Ormaz
- Lords of Ormaza
- Lords of Orme
- Lords of Oropesa
- Lords of Orozco
- Lords of Orsigny
- Lords of Ortilla
- Lords of Orval
- Lords of Orville
- Lords of Ossun
- Lords of Ostendorf
- Lords of Ottaiano
- Lords of Oultremont
- Lords of Ourton
- Lords of Ousselghem