| Orav, Maria | Estonia WU17 |  Estonia | Defender |
| Orbaiz, Pablo | Rubin (RUS) |  Spain | Midfield |
| Ordasi, Gergő | Hungary U17 |  Hungary | Goalkeeper |
| Ordega, Francisca | Rossiyanka (RUS) |  Nigeria | Forward |
| Ordets, Ivan | Illychivets (UKR) / Ukraine U21 |  Ukraine | Defender |
| Öreg, Cintia Mónika | Hungary WU17 | Hungary | Forward |
| Oremo, Johan | Gefle (SWE) |  Sweden | Forward |
| Orestes | Veria (GRE) |  Brazil | Defender |
| Orhan, Ak | Elazığspor (TUR) |  Turkey | Defender |
| Orhan, Belma | Sarajevo (BIH) / Bosnia and Herzegovina WU19 |  Bosnia and Herzegovina | Defender |
| Orhan Gülle | Gaziantepspor (TUR) / Turkey U21 | Turkey | Midfield |
| Orhan Şam | Fenerbahçe (TUR) | Turkey | Defender |
| Origi, Divock | LOSC (FRA) / Belgium U19 |  Belgium | Midfield |
| Orikhovskiy, Pavlo | Ukraine U17 | Ukraine | Midfield |
| Oriol, Eduardo | Zaragoza (ESP) | Spain | Forward |
| Oriol Romeu | Chelsea (ENG) / Spain U21 | Spain | Midfield |
| Orkan Çinar | Turkey U17 | Turkey | Midfield |
| Orkun Uşak | Mersin (TUR) | Turkey | Goalkeeper |
| Orlinov, Marin | Bulgaria U19 |  Bulgaria | Goalkeeper |
| Orlov, Jakob | Gefle (SWE) | Sweden | Forward |
| Orlova , Valentina | Russia WOCO |  Russia | Defender |
| Ørntoft, Christina | Malmö (SWE) / Denmark WOCO |  Denmark | Defender |
| Oroş, Cristian | Rapid Bucureşti (ROU) |  Romania | Defender |
| Orosa, Cristhian | Andorra U21 |  Andorra | Defender |
| Orozco, Yohandry | Wolfsburg (GER) |  Venezuela | |
| Orozco, Daniel | Asteras (GRE) | Spain | Defender |
| Oršić, Mislav | Inter Zaprešić (CRO) / Croatia U21 |  Croatia | Forward |
| Oršula, Filip | Wigan (ENG) / Slovakia U21 |  Slovakia | Midfield |
| Ortega Salinas, Jorge Miguel | Legia (POL) |  Paraguay | Midfield |
| Ortega-Jurado, Alina | Germany WU17 |  Germany | Forward |
| Ortiz | Interviú (ESP) / Spain FUT | Spain | Defender |
| Ortiz, Laura | Spain WU19 | Spain | Forward |
| Ortiz, Celso | AZ (NED) | Paraguay | Midfield |
| Ortlechner, Manuel | Austria Wien (AUT) / Austria |  Austria | Defender |
| Örün, Erdinc | Hamburg (GER) | Germany | Forward |
| Osaj, Leutrim | Nafta (SVN) / Albania U21 |  Albania | Midfield |
| Osanga, King | Sochaux (FRA) | Nigeria | Midfield |
| Osborn, Grant | England FUT |  England | Forward |
| Osborn, Ben | England U19 | England | Midfield |
| Osbourne, Isaac | Aberdeen (SCO) | England | Midfield |
| Oscar | Chelsea (ENG) | Brazil | Midfield |
| Óscar Cardozo | Benfica (POR) | Paraguay | Forward |
| Óscar González | Valladolid (ESP) | Spain | Midfield |
| Oscar Neira | Encamp (AND) / Andorra FUT | Andorra | Forward |
| Ose, Ilze | Skonto (LVA) |  Latvia | Midfield |
| Ose, Camilla | Røa (NOR) / Norway WU17 |  Norway | Forward |
| Osei, Kevin | Marseille (FRA) |  France | Midfield |
| O'Shaughnessy, Daniel | Finland U19 |  Finland | Defender |
| Oshchypko, Igor | Karpaty (UKR) | Ukraine | Defender |
| O'Shea, John | Sunderland (ENG) / Republic of Ireland |  Republic of Ireland | Defender |
