WWE and UFC have completed a £17.3bn merger and launched under a new name, TKO.
UFC owners Endeavour Group Holdings control 51% of the new public trading company, TKO Group Holdings, while WWE shareholders have 49%.
The business is led by Endeavour chief executive Ari Emanuel.
"The creation of TKO marks an exciting new chapter for UFC and WWE as leaders in global sports and entertainment," said Emanuel.
"With UFC and WWE under one roof, we will provide unrivalled experiences for more than a billion passionate fans worldwide."
Dana White has become the UFC's new CEO and Vince McMahon has been appointed as TKO's new executive chairman.
In a statement to announce the completion of the merger, TKO said: "TKO brings together UFC, the world's premier mixed martial arts organisation, and WWE, an integrated media organisation and the recognised global leader in sports entertainment, to create a new premium sports and entertainment company serving more than one billion young and diverse fans, reaching viewers in 180 countries, and producing more than 350 annual live events."
McMahon, whose January return to the WWE board followed his 2022 retirement amid misconduct claims, added: "This is the culmination of a decades-long partnership between Endeavor and WWE across strategic initiatives including talent representation and media rights.
"Given our collaborative, trusted relationship and Endeavor's incredible track record of success growing UFC, we believe WWE is optimally positioned for future growth and success as part of TKO.
"Our focus remains on delivering for our fans across the globe as we take the business to the next level alongside UFC and Endeavor."
WWE has a global reach and fanbase. The company had more than 16 billion social media video views in the final quarter of 2022. It has nearly 94 million YouTube subscribers and has more than 20 million followers on TikTok.
Five of its female wrestlers are in the world's top 15 most-followed female athletes across Facebook, Twitter and Instagram, led by former UFC fighter Ronda Rousey, who has 36.1 million followers.
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