- Northumbria
- Northup
- Norton
- Norval
- Norvell
- Norwood
- Nothnagle
- Nott
- Nourse
- Novak
- Novell
- Novotny
- Nowell
- Nowels
- Noyes
- Nuby
- Nuckolls
- Nuckols
- Nugent
- Nuhfer
- Numelin
- Nunally
- Nunziato
- Nurnberg
- Nusink
- Nuttall
- Nuttle
- Nuzzo
- Nycholls
- Nye
- Nylander
- O'Bannon
- O'Brien
- O'Brion
- O'Bryant
- O'Callaghan
- O'Connell
- O'Connor
- O'Daniel
- O'Dea
- O'Dell
- O'Donnell
- O'Driscoll
- O'Farrell
- O'Flaherty
- O'Hara
- O'Hearn
- O'Kelly
- O'Kerns
- O'Leary
- O'Malley
- O'Neal
- O'Neil
- O'Reilly
- O'Rourke
- O'Shea
- O'Toole
- Oakes
- Oakley
- Oakman
- Oaks
- Ober
- Oberg
- Oberhansly
- Oberst
- Ockey
- Oddo
- Odekirk
- Odell
- 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