| Competition: | 3. Liga |
| Season: | 2009–10 |
| Winners: | Osnabrück |
| Promoted: | Osnabrück Erzgebirge Aue |
| Relegated: | Borussia Dortmund II Wuppertal Holstein Kiel |
| League Topscorer: | Régis Dorn (22) |
| Biggest Home Win: | CZ Jena 6–0 Bayern II Ingolstadt 6–0 Burghausen |
| Biggest Away Win: | Bayern II 0–5 Regensburg |
| Highest Scoring: | Wuppertal 5–3 Kiel Wuppertal 5–3 Bayern II |
| Matches: | 380 |
| Total Goals: | 1023 |
| Prevseason: | 2008–09 |
| Nextseason: | 2010–11 |
The 2009–10 3. Liga season was the second season for the newly formed tier III of the German football league system. The season began on 25 July 2009 and ended on 8 May 2010.
2008–09 3. Liga champions 1. FC Union Berlin and runners-up Fortuna Düsseldorf were directly promoted to the 2. Bundesliga. They were replaced by FC Ingolstadt 04 and SV Wehen Wiesbaden, who finished in the bottom two places after the previous season.
Third-placed team SC Paderborn 07 were also promoted after defeating the 16th-placed team from last year's 2nd Bundesliga, VfL Osnabrück, in a relegation playoff. As a result, Osnabrück would play in 3. Liga.
VfR Aalen and Stuttgarter Kickers were relegated after finishing the 2008–09 season in the bottom two places. 18th-placed SV Wacker Burghausen were eventually spared from relegation after 5th-placed Kickers Emden voluntarily retracted their application for a license because of financial issues.[1] Emden will play in the fifth-tier Oberliga Niedersachsen.
The three relegated teams were replaced by the champions of the three Regionalliga divisions, Holstein Kiel (North), Borussia Dortmund II (West) and 1. FC Heidenheim 1846 (South).
| Team | Outgoing manager | Manner of departure | Date of vacancy | Replaced by | Date of appointment | Position in table | |
|---|---|---|---|---|---|---|---|
| VfL Osnabrück | Claus-Dieter Wollitz | FC Energie Cottbus purchased rights | 30 June 2009[3] | Karsten Baumann | 1 July 2009[4] | Pre-Season | |
| FC Carl Zeiss Jena | Marc Fascher | End of contract | 30 June 2009 | René van Eck | 1 July 2009 | Pre-Season | |
| FC Rot-Weiß Erfurt | Henri Fuchs | End of tenure as caretaker | 30 June 2009 | Rainer Hörgl | 1 July 2009 | Pre-Season | |
| VfB Stuttgart II | Rainer Adrion | New coach of Germany U-21 | 30 June 2009 | Reiner Geyer | 1 July 2009 | Pre-Season | |
| SV Wacker Burghausen | Ralf Santelli | End of contract | 30 June 2009 | Jürgen Press | 1 July 2009 | Pre-Season |
Source: Kicker magazine
Michael Holt (Holstein Kiel) Sven Schipplock (VfB Stuttgart II) Tobias Schweinsteiger (SpVgg Unterhaching)
Najeh Braham (Erzgebirge Aue)
Tore Andreas Gundersen (Dynamo Dresden)Björn Lindemann was named as player of the season
