The one that started it all back in 2010 when the world needed to know who the greatest Tetris player in the world was. And since it's inception, it continues to just get bigger and better with each passing year. The tournament has gained popularity for its intense matches, skilled players, and vibrant Tetris community. Players compete on the original Nintendo Entertainment System (NES) version of Tetris, using classic hardware and controllers. The CTWC has become a significant event in the competitive Tetris scene, attracting both participants and viewers globally every year.
In its sixth year, Classic Tetris Monthly stands as the premier and longest-running online tournament, serving as a training ground for aspiring World Champions. The top 16 qualifiers worldwide engage in a fiercely competitive single-elimination, best-of-five tournament. Renowned for its intense competition, records are consistently broken each month. Participants not in the top bracket join "lower" tournaments, emphasizing fun and occasionally seeking vengeance.
Classic Tetris Gauntlet is an online Competetive Scene for Classic Tetris (NES) Founded By ITZsharky and is hosted on Twitch!
Classic Tetris Brawl is a quarterly online NES Tetris tournament first held in 2019 and was created by former 2 time world champion DogPlayingTetris.
Classic Tetris Wars is a tournament series founded in 2021 that focuses on eight player matches in different formats and founded by Dan Woods of Grand Designs
World Puzzle League is an organization created by BeastinShen covering NES Tetris and different Tetris games and providing tournament coverage. WPL is built with regional LAN events in mind. Online weekly tournaments hosted on Puyo-Puyo Tetris (PC and Switch) and Tetr.io.
Here is a great list put together by CTM linking to discords of the lesser known online Tetris competitions.