The WWE and the UFC are merging into one ... now forming a $21 billion company.
Endeavor, the parent co. of UFC, announced the move on Monday morning ... revealing its shareholders will own 51 percent of the new org. WWE shareholders, meanwhile, will own 49 percent.
Vince McMahon will hold the title of Executive Chairman of the Board with the new group -- while Dana White will continue as the President of UFC. Ariel Emanuel, the CEO of Endeavor, will be the head honcho of it all.