- Odom
- Odronic
- Oefinger
- Oehmke
- Oelkers
- of Acre
- of Alkborough
- Lucia

(Abt 1065-Abt 1138)
- of Anjou
- of Antwerp
- of Aquitaine
- of Bellême
- of Brittany
- of Brotherton
- of Caen
- of Castile
- of Chester
- of Clarence
- of Dublin
- of Dunbar
- of England
- of Flanders
- of France
- of Galloway
- Helen (Abt 1208-Aft 1245)
- of Gloucester
- of Guelders
- of Hainault
- of Huntingdon
- of Italy
- of Lancaster
- of Lens
- of Luxembourg
- of Normandy
- of Northumberland
- Alice

(Est 1074-Aft 1126)
- of Poitou
- of Provence
- of Salisbury
- of Scotland
- of Woodstock
- Ogburn
- Ogden
- Ogilvie
- Ogilvy
- Ogle
- Ogles
- Oglesby
- Ohl
- Ohlson
- Ohzourk
- Ojers
- Olcott
- Oldaker
- Olden
- Oldfield
- Oldham
- Oldroyd
- Olds
- Olejnik
- Olin
- Oliphant
- Olive
- Oliver
- Oliveria
- Olivet
- Olivier
- Olk
- Olmstead
- Olmsted
- Olney
- Olpin
- Olsen
- Olson
- Onley
- Openshaw
- Oppelt
- Orchard
- Orcutt
- Orgill
- Oricchio
- Oringer
- Orme
- Orndorf
- Orpin
- Orput
- Orr
- Orth
- Orton
- Orvice
- Orvin
- Orvis