Floyd Mayweather's bout with Shane Mosley is set to go ahead on May 1 after the six-time world champion signed the contract.
In a statement released by Swanson Communications, Mayweather confirmed he would take on Mosley at Las Vegas' MGM Grand.
With Mosley already having signed the papers, Mayweather's signature was the final piece in the jigsaw.
The 32-year-old welterweight said: "This one is definitely for the fans as I wasn't going to waste anyone's time with a meaningless tune-up bout and asked to fight Shane immediately.
"I have said ever since I came back to the sport that I only wanted to fight the best. I think Shane is one of the best, but come May 1, he still won't be great enough to beat me.
Mosley was delighted to have the final details confirmed and predicted he would have little trouble inflicting the first defeat of Mayweather's career.
"I have always wanted to fight Floyd and now it is finally coming true," he said.
"I am already in great shape and ready to show everyone on May 1 that I am stronger, faster and better than he is. I will have no problem beating him."
The fight will also take place under strict anti-doping procedures championed by the Mayweather camp.
Leonard Ellerbe, chief executive of Mayweather Promotions, said: "Floyd has been trying to make this fight for the last 10 years, so he is extremely excited about the opportunity to face Shane. He can't wait to extend his undefeated record and perform at the highest level.
"More importantly, he is also happy to set the precedent for random blood testing in order to ensure fair and safe contests for all fighters."
Fellow promoters Golden Boy were also keen to talk up both the bout and the anti-doping measures.
Richard Schaefer, Golden Boy CEO, said: "When two champions of this calibre meet in the ring, you can expect nothing but excellence and that is what we are going to see on May 1.
"Shane Mosley is one of the greatest fighters of this era and I commend him for not only agreeing to the fight against Mayweather, but also agreeing to participate in a testing process that can only help the integrity of the sport.