| Clubname: | Olympiacos B |
| Fullname: | Olympiacos Football Club B |
| Founded: | 2021 |
| Dissolved: | 2024 |
| Ground: | Rentis Training Centre |
| Capacity: | 3,000 |
| Season: | 2023–24 |
| Position: | Super League Greece 2, 10th (relegated) |
Olympiacos Football Club B, or simply Olympiacos B (Ολυμπιακός Β), was the reserve team of Greek club Olympiacos.
The stadium that hosts in Olympiacos B was the Rentis Training Centre with a capacity of 3,000.
In the season 2023–24 of Super League 2,Olympiacos B finished 10th hence was relegated to Gamma Ethniki,the third highest football league in Greece.However,clubs in Gamma Ethniki can only consist of amateur players since it's an amateur division,hence no professional players can play in the reserve team of Olympiakos which was the case in the past for players like Youssef El Arabi,Kostas Fortounis e.t.c. and young players like Apostolopoulos