| Club: | Olympiacos |
| Season: | 2009–10 |
| Manager: | Temuri Ketsbaia (until 25 November 2009) Zico (until 1 March 2010) Božidar Bandović |
| Chairman: | Sokratis Kokkalis |
| Stadium: | Karaiskakis Stadium, Piraeus |
| League: | Super League Greece |
| League Result: | 2nd in regular season (5th in play-offs) |
| Cup1: | Greek Cup |
| Cup1 Result: | Fourth round |
| Cup2: | Champions League |
| Cup2 Result: | Round of 16 |
| League Topscorer: | Kostas Mitroglou (9) |
| Season Topscorer: | Kostas Mitroglou (14) |
| Highest Attendance: | 31,059 vs Panathinaikos (29 November 2009) |
| Lowest Attendance: | 16,056 vs Kavala (12 September 2009) |
| Average Attendance: | 19,666 |
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| Prevseason: | 2008–09 |
| Nextseason: | 2010–11 |
The 2009–10 season was Olympiacos's 51st consecutive season in the Super League Greece and their 84th year in existence. Olympiacos finished 2nd in the regular season of the Greek Super League and ranked last at the play-off games, resulting in a 5th place at the League, the worst position of team's recent seasons. Olympiacos also participated in UEFA Champions League 2009–10, and managed to qualify to the knock-stage (round of 16). They lost twice from French side Bordeaux, 3–1 on aggregate.
This season was the last season with Sokratis Kokkalis as chairman of the club. The 5th league position as well as the team's low level of spectacle created a disappointing atmosphere, resulting in Kokkalis's decision to leave the club after two decades of constant presence.
| EU Nationals | Non-EU Nationals |
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As on: 21 August 2009,Source: Olympiacos F.C. U21 Team
In:
Out:
Total income: €5 million
See main article: 2009–10 Super League Greece.
All times at EET
See main article: 2009–10 Greek Football Cup.
All times at EET
See main article: 2009–10 UEFA Champions League.
All times at EET
All times at EET
All times at EET
Standings
See main article: 2009–10 UEFA Champions League knockout stage.
All times at EET