RPGA
The RPGA (also called the Role Playing Game Association and the RPGA Network at various times), was initially part of the organized play arm of TSR, Inc and then Wizards of the Coast. From 1980 to 2014, it organized and sanctioned role-playing games worldwide.
The D&D Adventurer's League program is WotC's successor to the RPGA for organized play campaigns.
See the Wikipedia article for more information.