Football referees
Ozan Ergün
Oleg Evstigneev
Olsid Ferataj
Oliver Fluch
Oscar Forsberg
Omar Gallo
Oleksii Garkusha
Ondřej Ginzel
Oğuzhan Gökçen
O. Goldrick
Oscar Javier Gómez Flórez
Orel Grinfeeld
Onur Güneş
Oleg Gurchenko
Oleg Gusakov
Ovidiu Alin Hațegan
Oleg Igorevich Zhuravlev
Osama Ismail
O. Jantunen
Oh-Hyeon Jeong
Oscar Johnson
Oleksandr Kalyonov
Orhan Karaboğa
Okan Kayataş
Ola Kellerhals
Omar Khaild
Oleg Kogut
Osman Köksaldı
Oleg Koretskiy
Osiase William Koto
Oleksandr Kovalenko
Orlando Kuka
O. Kwinda
Oliver Langford
Owen Lawrence
Ondřej Lerch
Oliver Lossius
Oliver Mackey
Óscar Maldonado Urey
Óscar Mejía García
Othusitse Modise
Osman Mohammadi
Oscar Moncada
Oliver Moran
Orxan Məmmədov
Odeh Na'al
Ori Nakel
Oshane Nation
Ola Nielsen
Ola Hobber Nilsen