UFC co-owner Lorenzo Fertitta confirmed the news to ESPN.com Tuesday, after an initial report by the Los Angeles Times. The five-round, non-title fight will headline an unannounced UFC event at the MGM Grand Garden Arena.
"It's a long-term deal exclusive to the UFC," Fertitta said. "Alistair is known to bounce around in K-1, Dream and Strikeforce, but he's now exclusively signed to the UFC.
"At the end of the day, he's one of the best in the world. Now we get to see how he matches up against (UFC) guys. We have a tremendous heavyweight division and bringing him along makes it stronger."
Overeem (35-11), who has held belts in multiple promotions, was released from Strikeforce in July despite having one fight remaining on his contract. At that time, he entered an exclusive negotiating period with Zuffa, parent company of Strikeforce and the UFC.
During negotiations, the UFC offered an immediate title fight against the winner of a Nov. 12 matchup between Cain Velasquez and Junior Dos Santos. Overeem ultimately turned down the opportunity in favor of fighting again in 2011.
"I'm a fighter who wants to fight a lot," Overeem said. "If I had to wait for a title fight, I'd basically be waiting until next year. They came up with this option and I wanted it.
"I'm very excited to fight Brock. He's a big guy. We have different styles. I think it's going to be very exciting for fans."
Lesnar (5-2) has been out of action since a first-round TKO loss to Velasquez last October due to a second bout with diverticulitis, an intestinal disorder.
Several reports surfaced earlier this month indicating Lesnar's medical problems were forcing him toward retirement. UFC president Dana White dismissed those claims as "ridiculous" during a national media call on Sept. 2.
With Lesnar set to return to the Octagon and Overeem not wanting to wait on the title fight, Fertitta said pairing the two became an easy call.
"We wanted him to fight for the heavyweight championship but it didn't work out with that fight happening on Nov. 12," Fertitta said. "He didn't want to wait around. To his credit, he wants to fight the best. Brock is a huge name guy."
Overeem's long-term deal could be a good sign for his Golden Glory teammates.
When the heavyweight was released, several of his stable mates were dismissed as well, most notably former women's 135-pound Strikeforce champion Marloes Coenen. Coenen has since signed with North Carolina-based BlackEye Promotions.
White cited a disagreement in business practices as the cause for cutting the Golden Glory fighters. On the heels of Overeem's deal, however, Fertitta described Zuffa's relationship with Golden Glory as "perfect," and added talks regarding other fighters would soon take place.
"That was a dispute but I'm sure talks are going on with them now as well," Overeem said. "It will be resolved."
Brett Okamoto covers mixed martial arts for ESPN.com.