Britain’s Amir Khan will fight Mexico’s Saul Alvarez for the WBC world middleweight title on 7 May in Las Vegas.
Khan, 29, a former light-welterweight world champion, has not fought since outpointing Chris Algieri in New York in May.
Alvarez, 25, beat Miguel Cotto by a unanimous points decision to claim the title in Las Vegas in November.
Alvarez has lost once and won 46 of his 48 fights.
The fight has been set at a catchweight of 155lb, eight more than Khan weighed in victory against Algieri and a jump of two weight divisions.
The usual weight limit for middleweight is 160lb, but Alvarez’s last few fights have had the same weight stipulation.
Khan’s announcement also rules him out of a fight against IBF welterweight champion and domestic rival Kell Brook at Wembley on June 4.
“I know Canelo fights the best and wouldn’t pass up the opportunity to face me like others have,” said Khan. “My goal is to always fight the biggest names and the best fighters. That is why I’m excited for this fight.
“I know I have the speed and ability to beat him and will give my fans what they deserve.”
“As the middleweight champion of the world, I will take on the best fighters in the sport and on Cinco De Mayo weekend, I look forward to making the first defence of my titles,” said Alvarez.
“Amir was a decorated amateur, a two-time world champion and is in the prime of his career. Fans are in for a great fight.”