- Octavio MarettoPosition: shooting guardNationality: Italy, Argentina
- Octavio VidalesBorn: 2 April 1965Sport: association football
- Odalys RivasPosition: midfielder, defenderBorn: 9 October 1998
- Olienka SalinasPosition: forwardBorn: 16 November 1973
- Oliver LópezPosition: midfielderBorn: 20 May 2008
- Oliver RiveraPosition: centre-backBorn: 7 March 2002
- Omar CuyaPosition: defenderBorn: 2 September 1981
- Omar ReyesPosition: midfielderBorn: 13 December 1988
- Omar ZegarraPosition: defenderBorn: 6 August 1980
- Orazio SapienzaNationality: ItalyBorn: 16 December 1994
- Orestes JordánPosition: defenderBorn: 21 November 1913
- Orlando AllendePosition: forwardBorn: 9 January 1988
- Orlando de la TorrePosition: defenderBorn: 21 November 1943
- Orlando MendutoNationality: ItalyBorn: 18 January 1976
- Orlando PradoPosition: defenderBorn: 16 February 1972
- Oscar AlbuquerquePosition: midfielderBorn: 4 September 1954
- Oscar BrocchiNationality: ItalyBorn: 13 October 1968
- Oslimg MoraPosition: wing halfBorn: 2 June 1999
- Osnar NoronhaPosition: forwardBorn: 17 December 1991
- Osondu James ForchettaNationality: ItalyBorn: 10 February 2009
- Oswaldo AraujoPosition: forwardBorn: 3 October 1964
- Oswaldo RamírezPosition: forwardBorn: 28 March 1947
- Otis RealeNationality: ItalyBorn: 16 October 1998
- Oumar FallNationality: Senegal, ItalyBorn: 24 December 2007
- Óscar ArizagaPosition: defenderBorn: 20 August 1957
- Óscar CalvoPosition: forwardBorn: 22 June 1964
- Óscar del PortalPosition: midfielderBorn: 9 January 1982
- Óscar GuerraPosition: defenderBorn: 25 March 1985
- Óscar GugliottaPosition: shooting guardNationality: Dominican Republic, Italy
- Óscar Gómez SánchezPosition: forwardBorn: 31 October 1934
- Óscar IbáñezPosition: goalkeeperBorn: 8 August 1967
- Óscar PintoPosition: midfielderBorn: 20 January 2002
- Óscar Ruiz CorralesPosition: defenderBorn: 7 December 1985