The 2009–10 Liga III season was the 54th season of Liga III, the third tier of the Romanian football league system. The season started on August 21, 2009 and ended on June 4, 2010.
The winners of each division got promoted to the 2010–11 Liga II season.
The bottom six from each division were relegated at the end of the season to the county football leagues (Liga IV). From the 12th placed teams, another one was relegated. To determine this team, separate standings were computed, using only the games played against the clubs ranked 1st through 11th.
^ abFotbal Oil Terminal Constanța and Utchim Găești withdrew from the championship during the second half and will lose all remaining matches with 0–3.
^ abcViitorul Toporu, Victoria Adunații Copăceni and Filipeștii de Pădure withdrew from the championship during the second half and will lose all remaining matches with 0–3.[1][2]
^Petrolul Teleajen Ploiești was excluded from the championship during the second half and will lose all remaining matches with 0–3.[3]
^Predeal withdrew from the championship during the winter break and will lose all remaining matches with 0–3.[4]
^Pandurii Târgu Jiu were relegated at the end of 2009–10 Liga I season and will play in 2010–11 Liga II. Since reserve teams are not allowed to play in the same league tier as their first teams, Pandurii Târgu Jiu II, Pandurii's reserve team, were not promoted to Liga II despite finishing as champions. Instead, second-placed ACU Arad were promoted.
^"AFC Filipeștii de Pădure s-a retras oficial!" [AFC Filipeștii de Pădure has officially withdrew!]. liga2.prosport.ro. 30 March 2010. Archived from the original on 11 September 2022. Retrieved 11 September 2022.(in Romanian)
^"Exclusiv! Se retrage și Copăceniul!" [Exclusive! Copăceni is also withdrawing!]. liga2.prosport.ro. 7 April 2010. Archived from the original on 20 September 2021. Retrieved 11 September 2022.(in Romanian)
^"Retezatul Hațeg s-a retras din campionat!" [Retezatul Hațeg withdrew from the championship!]. liga2.prosport.ro. 25 March 2010. Archived from the original on 11 September 2022. Retrieved 11 September 2022.(in Romanian)
^"Turul Micula se retrage din campionat" [Turul Micula withdrew from the championship]. liga2.prosport.ro. 31 March 2010. Archived from the original on 18 November 2021. Retrieved 11 September 2022.(in Romanian)