| Oehrli, Jennifer | Zuchwil (SUI) / Switzerland WOCO |  Switzerland | Goalkeeper |
| O'Farrelly, Sinead | Republic of Ireland WU19 |  Republic of Ireland | Defender |
| Oferil, Marc | Andorra FUT |  Andorra | Defender |
| Offenbacher, Daniel | Wiener Neustadt (AUT) |  Austria | Midfield |
| Ofori-Appiah, Willem | Genk (BEL) |  Belgium | Defender |
| Ogbiagbevha, Emueje | BIIK (KAZ) |  Nigeria | Forward |
| Ogbonna, Angelo | Torino (ITA) / Italy |  Italy | Defender |
| Oggesen, Andreas | Denmark U19 |  Denmark | Midfield |
| Oghinciuc, Costin | Gloria Bistriţa (ROU) |  Romania | Goalkeeper |
| Ogilvie, Connor | England U17 |  England | Defender |
| Ogimi, Yuki | Potsdam (GER) |  Japan | Forward |
| Ogleby, Robert | Wrexham (WAL) / Wales U21 |  Wales | Forward |
| O'Gorman, Aine | Peamount (IRL) / Republic of Ireland WOCO | Republic of Ireland | Forward |
| Ogu, John | Académica (POR) | Nigeria | Midfield |
| Ogunjimi, Marvin | Beerschot (BEL) | Belgium | Forward |
| Oguz Daglaroglu | Akhisar (TUR) |  Turkey | Goalkeeper |
| O'Hagan, Catherine | Glentoran (NIR) / Northern Ireland WOCO |  Northern Ireland | Forward |
| Öhagen, Hjalmar | Gefle (SWE) |  Sweden | Midfield |
| O'Halloran, Michael | Scotland U21 |  Scotland | Forward |
| O'Halloran, Dean | Republic of Ireland U17 | Republic of Ireland | Midfield |
| Ohana, Daniel | Israel WU19 |  Israel | Goalkeeper |
| O'Hanlon, Ben | England U17 | England | Defender |
| Ohanyan, Albert | Armenia U21 |  Armenia | Goalkeeper |
| O'Hara, Mark | Scotland U19 | Scotland | Defender |
| Ohayon, Matan | Charleroi (BEL) | Israel | Midfield |
| Ohi Kwoeme | Lillestrøm (NOR) / Norway U19 |  Norway | Midfield |
| Ohlsson, Maja | Sweden WU19 | Sweden | Goalkeeper |
| Ohlsson, Nellie | Sweden WU17 | Sweden | Defender |
| Öhman, Ludvig | Kalmar (SWE) / Sweden U21 | Sweden | Defender |
| Ohno, Shinobu | Lyon (FRA) | Japan | Forward |
| Öhrström, Stéphanie | Verona (ITA) | Sweden | Goalkeeper |
| Oier | Osasuna (ESP) |  Spain | Defender |
| Oier Olazábal | Barcelona (ESP) | Spain | Goalkeeper |
| Õigus, Eneli | Estonia WU19 |  Estonia | Defender |
| Oikarinen, Velma | PK-35 (FIN) |  Finland | Goalkeeper |
| Oikonomou, Vangelis | Ross County (SCO) |  Greece | Defender |
| Oikonomou, Kostas | Greece U17 | Greece | Defender |
| Õisma, Kairi | Estonia WU17 | Estonia | Defender |
| Ojala, Mika | Häcken (SWE) / Finland | Finland | Midfield |
| Ojala, Juhani | Terek (RUS) / Finland | Finland | Defender |
| Ojala, Grete | Pärnu (EST) / Estonia WOCO | Estonia | Defender |
| Ojala, Matias | Finland U19 | Finland | Midfield |
| Ojamaa, Henrik | Motherwell (SCO) / Estonia | Estonia | Forward |
| Ojanperä, Juha | Ilves (FIN) / Finland FUT | Finland | Goalkeeper |
| Ojanperä, Rami | Finland U17 | Finland | Midfield |
| Ojanperä, Aleksi | Finland U17 | Finland | Defender |
| Ojo, Funso | Beerschot (BEL) / Belgium U21 | Belgium | Midfield |
| Ojo, Oluwaseyi | England U17 | England | Midfield |
| Ojo, Kim | Genk (BEL) | Nigeria | Forward |
| Okan Alkan | Kayserispor (TUR) / Turkey U21 | Turkey | Defender |
