There are 65 unique male surnames beginning with O:

O'Brian	O'Briant	O'Brien	O'Bryant	O'Harra	O'Neal	Oates
Obbe	Obee	Obenour	Ober	Oberdier	Oberly	Odell
Offerbaker	Ogan	Oglesby	Ohaver	Ohler	Ohnsman	Oiler
Okey	Oldaker	Oldoerp	Olds	Oliphant	Olive	Oliver
Oller	Olmsted	Olson	Olssom	Oman	Opphile	Oppihle
Orahood	Oram	Organ	Orley	Ormeroid	Orr	Orstern
Orth	Osborn	Osborne	Osbun	Osswald	Ostrom	Oswald
Ott	Otte	Ousler	Outland	Overacker	Overfield	Overholser
Overhot	Overly	Overturf	Owen	Owens	Owry	Owston
Oxley	Oyler

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