April 3 (Reuters) - World Wrestling Entertainment Inc (WWE.N) will combine with Endeavor Group-owned (EDR.N) mixed martial arts franchise UFC to form a new, publicly listed entertainment giant valued at about $21 billion, the companies said on Monday. Hollywood power broker and Endeavor CEO Ari Emanuel will take the helm at the merged entity. In January, WWE said it would explore strategic options that could include a sale, shortly after long-time CEO McMahon's return to the company. McMahon had retired in July last year as the company's CEO and chair, following an investigation into his alleged misconduct. Co-CEO Stephanie McMahon, who single-handedly managed the mantle when her father exited, resigned a week after he returned in January.

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