Canelo Alvarez, 28, agreed to a five-year, 11-fight contract with streaming platform DAZN on Wednesday that will pay him a minimum of $365 million, according to a press release.
Alvarez's new contract is being described as the biggest in sports history by ESPN.
Mayweather himself looks to be eyeing up another massive pay day, telling TMZ Sports this week that a fight with UFC champion Khabib Nurmagomedov was "happening" and that he would get a "nine-figure payday".
Alvarez will challenge Rocky Fielding on DAZN's platform on December 15 at Madison Square Garden.
It will offer fans a monthly subscription service to watch the fights rather than having to pay hefty pay-per-view fees.
Alvarez and Britain's Fielding will hold a news conference in NY on Wednesday to promote their fight at Madison Square Garden.
His contract surpasses that of Giancarlo Stanton, who signed a 13-year, $325 million pact with the Miami Marlins in 2014. I am moving up in weight and I don't know how my body will feel. However, HBO recently announced that it would be bowing out of boxing after 45 years showing some of the sport's biggest fights, paving the way for DAZN to swoop for coverage of Canelo's bouts.
As part of the partnership, Golden Boy Promotions will put on up to 10 high-caliber fight nights per year that will stream live on DAZN beginning in early 2019.
"I always want to take on challenges, and I am very happy my fans will be able to see me fight for a small cost".
That deal included a total of 16 bouts each year across the United States on top of Matchroom's existing 16 fight nights in the UK.
His last bout - a win in a rematch with Gennady Golovkin on 15 September - generated HBO an estimated $121m (£92m).
It has already signed another top flight boxer when it inked a deal with Anthony Joshua, who holds the IBF, WBA and WBO heavyweight belts.
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