| Surname | Individuals |
|---|---|
|
O'Brien
|
5 |
|
O'Bryne
|
1 |
|
O'Toole
|
2 |
|
Oblinus
|
1 |
|
Ochus
|
2 |
|
Odder
|
1 |
|
Odeanal
|
3 |
|
Ogilvie
|
9 |
|
Ogilvy
|
2 |
|
Ogstoun
|
2 |
|
Olafsson
|
1 |
|
Olcott
|
2 |
|
Oldham
|
1 |
|
Olesen
|
15 |
|
Oliver
|
4 |
|
Olivo
|
1 |
|
Olofsdotter
|
2 |
|
Olofson
|
1 |
|
Olson
|
2 |
|
Onley
|
1 |
|
Orchard
|
1 |
|
Orne
|
1 |
|
van Orsdoll
|
15 |
|
Orten
|
1 |
|
Orton
|
1 |
|
Osborne
|
1 |
|
Osmon
|
1 |
|
Ouldham
|
1 |
|
Overgaard
|
1 |
|
ap Owain
ferch Owain |
3 1 4 |
|
ab Owain Gwynedd
|
1 |
|
Owen
|
15 |
|
Owens
|
1 |
|
Ower
|
1 |
|