The Waterbending Duelist League (WDL) is a competitive sporting organization founded in the Southern Water Tribe in 211 AG by Kantu. It consists of waterbenders, primarily of the South Pole, facing off against one another in duels throughout a regular season and eventually the playoffs. Both males and females have been allowed to compete since its establishment. One must be at least age 13 to compete in the WDL; those under it will be placed in the WDL Junior Division (WDLJD). Starting at age 13, WDL management has the right to promote anyone from the WDLJD to the main league if they have a significant competitive advantage; at age 16, anyone still in the WDLJD will be automatically moved up to the WDL.

The WDL has gone through multiple eras of strong competitors, but the league has always run on "parity", it tends to be that the #1 duelist does not win the league's championship. It has made the WDL the biggest recreational attraction in the Southern Water Tribe.