British WBA world super-middleweight champion Callum Smith will fight Saul 'Canelo' Alvarez on 19 December.
The fight will take place in the United States, with the venue still to be confirmed.
Mexican Alvarez is seen as one of the best fighters in boxing and has held world belts in four weight divisions.
Liverpudlian Smith, 30, is unbeaten in 27 fights, defending his world title twice since winning it from George Groves in 2018.
"I have wanted a big fight since becoming world champion, so I am pleased that during these challenging times we can deliver to the fans a fight between the very best in the division," Smith said.
"I truly believe I [will] beat him and will prove that 168lbs is my division."
Alvarez currently holds the 'regular' form of Smith's WBA super-middleweight belt and holds two belts at middleweight.
It will be a first fight in more than a year for 30-year-old Alvarez, who has only lost once in 56 bouts - against Floyd Mayweather in 2013.
"I'm very happy to return to the ring and continue to make history," said Alvarez, who has a 53-1-2 record.
"I am motivated to continue to be the best, and I look forward to fighting Callum Smith, who is one of the best at 168lbs."
Smith's last fight was also in November 2019, when he beat John Ryder in Liverpool.
Alvarez beat Smith's brother Liam in 2016.
Smith's promoter Eddie Hearn told BBC Newsbeat last week it would be "an honour" to fight a "pound-for-pound great" in Alvarez.
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