| Tashan Oakley-Boothe | c | ING | 2017/18 | 0 | 0 | Tottenham Hotspur | | | |
| Josef Obajdin | a | RCE | 1996/97 | 0 | 0 | Sparta Praha | | | |
| Mounir Obbadi | c | MAR | 2014/15 | 1 | 0 | Hellas Verona | | | |
| Dimitri Oberlin | a | CAM | 2018/19 | 0 | 0 | Empoli | | | |
| Adam Obert | d | SLV | 2021/22 | 1 | 0 | Cagliari | | | |
| Gabriel Obertan | c | FRA | 2010/11 | 0 | 0 | Manchester United | | | |
| Oberti | c | ITA | 1960/61 | 0 | 0 | Asti | | | |
| Joel Obi | c | NIG | 2009/10 | 8 | 0 | Chievo Verona, Inter, Parma, Salernitana, Torino | | | |
| John Obi Mikel | c | NIG | 2008/09 | 4 | 0 | Chelsea | | | |
| Pedro Obiang | c | SPA | 2010/11 | 9 | 0 | Sampdoria, Sassuolo | | | |
| Giuseppe Obici | a | ITA | 1919/20 | 1 | 0 | Modena | | | |
| Victor Obinna | a | NIG | 2005/06 | 1 | 0 | Chievo Verona, Inter | | | |
| Nwankwo Obiorah | c | NIG | 2010/11 | 1 | 0 | Inter, Parma | | | |
| Gábor Obitz | c | UNG | 1923/24 | 0 | 0 | Makkabi Brno | | | |
| Giorgio Oblach | d | ITA | 1956/57 | 0 | 0 | Reggina | | | |
| Jan Oblak | p | SLO | 2013/14 | 5 | -7 | Atlético Madrid, Benfica Lisbona | | | |
| Anthony Obodai | c | GHA | 2004/05 | 1 | 0 | Ajax Amsterdam | | | |
| Christian Obodo | c | NIG | 2002/03 | 10 | 0 | Fiorentina, Lecce, Perugia, Udinese | | | |
| Mauro Obolo | a | ARG | 2002/03 | 0 | 0 | Piacenza | | | |
| Abdulla Obran | c | EAU | 2002/03 | 0 | 0 | Al-Ain FC | | | |
| Jorge Obregón | a | COL | 2022/23 | 0 | 0 | Rijeka | | | |
| Andrew O'Brien | d | ING | 2002/03 | 2 | 0 | Newcastle United | | | |
| Branislav Obžera | c | SLV | 2008/09 | 2 | 0 | Artmedia Petržalka | | | |
| Lucas Ocampos | c | ARG | 2015/16 | 4 | 0 | Genoa, Milan, Olympique Marseille, Sevilla | | | |
| Enzo Occhetta | c | ITA | 1958/59 | 4 | 0 | Genoa, Milan | | | |
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