O
| James O'Brien | Player 2017-2018 |
2005 Republic of Ireland U19 1 cap 2006-2008 Republic of Ireland U21 6 caps |
| Diamuid O'Carroll | Player 2007 | 2006 Republic of Ireland U21 4 caps |
| Stephen O'Donnell | Player 2003-2004 |
1999-2000 Scotland U16 4 caps 2001 Scotland U19 1 cap 2002-2003 Scotland U20 2 caps |
| Kazeem Olaigbe | Player 2022-2023 |
2018 Belgium U15 4 caps 2018-2019 Belgium U16 11 caps 2019 Belgium U17 6 caps 2021-2022 Belgium U19 5 caps 2022 Belgium U20 2 caps 2023-2024 BelgiumU21 13 caps |