The Belgian Third Division (Dutch: Derde klasse, French: Division III) is the third highest level in Belgianfootball. It has two leagues of 18 teams each (A and B) at the same level. This competition, known as the Belgian Promotion was first played in the 1926-27 season with three leagues, then with four leagues between 1931 and 1952. From 1952 on, only two leagues remain and the competition is named the third division. Originally set to 16 clubs, the number of clubs in each division was increased in 2009 to 18 clubs. At the end of the regular season, both league winners promote to the second division and a play-off is played to determine a possible third club to promote. The champion of the third division is determined after a two-legged match between the winners of the two leagues. If those matches end in a draw, a third match is played on a neutral ground. However in recent years this final game has not been organized anymore due to lack of interest.
The competition comprises the regular season (two leagues of 18 teams, 34 matchdays each) followed by the third division play-off (7 teams, 3 matchdays). Each team plays 34 matches during the regular season (from August till May). The regular season is divided in 3 periods with the first period consisting of the first 10 match days, the second period consisting of the next 12 match days and the third period consisting of the final 12 match days. For each period in each league, a ranking is computed in the same way as the overall league rankings (three points for a win, one point for a draw and no point for a loss). In each league, the winner of the regular season promotes to the second division and the two worst-placed teams (17th and 18th) are relegated to the Promotion. The 16th placed teams must play the Promotion play-off with teams from Promotion (see Promotion).
The three period winners in each league qualify for the third division play-off along with the 16th-placed team in the second division. If the league winner also wins one or more period or that a period winner wins more than one period, finishes in the last three places or has not received a second division license, the best-placed teams in the league overall ranking qualify for the play-off so that 3 teams in each league qualifies. The playoff is played in three rounds. In the first round, the 6 qualifiers from the third division are drawn in three matches played in two legs. The winners of the first round and the 16th-placed team from the second division enter the second round (2 matches played in two legs). The final round is also played in two legs. The winner qualifies for the second division. In each round, the away goals rule is used to declare the winner in case of aggregate tie score. If each team has scored the same number of away goals, the teams play extra time of two 15-minutes periods. If there is still a tie, the away goals rule is applied once again. Finally, the matches go to penalties.