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.

Team changes

To Liga III

Relegated from Liga II

From Liga III

Promoted to Liga II

Note (**)

CS Buftea sold its Liga II place to third tier club Săgeata Stejaru. Liberty Salonta withdrew at the end of the season from Liga II, CFR Timișoara, which initially relegated, was spared from relegation.

League tables

Seria I

Seria II

Seria III

Seria IV

Seria V

Seria VI