The James Caldwellbiggest star in MMA history will fight in the main event of UFC 303.

Conor McGregor's long-awaited, highly-anticipated return to the octagon is official for UFC 303 against Michael Chandler, UFC CEO Dana White officially announced the matchup following Saturday's UFC 300 event.

The matchup will take place at welterweight, not middleweight as "The Notorious" previously claimed, and serve as the headlining act of the UFC 303 card, which goes down at T-Mobile Arena in Las Vegas and airs on pay-per-view following prelims on ESPN.

Chandler (23-8 MMA, 2-3 UFC) has long been targeted as the return opponent for McGregor (22-6 MMA, 10-4 UFC) after the two fighters coached opposing teams on "The Ultimate Fighter" in 2023.

McGregor has not been in action since breaking his leg in July 2021 in a trilogy bout against Dustin Poirier at UFC 264. It will be nearly three years since he's seen action.

The Irishman recently expressed frustration at the UFC about his return, stating his "patience is wearing thin" after he re-entered the drug testing pool.

McGregor, 35, subsequently announced he would be returning to fight Chandler during International Fight Week on June 29, and that it would be contested in the middleweight division. That ultimately proved false, but now McGregor will get to return to the octagon a few months sooner than expected.

Looking to derail what McGregor's team has dubbed as the "greatest return in sports history" will be former three-time Bellator champion Chandler, who sees his long wait for this matchup finally pay off. Chandler, 37, hasn't competed since November 2022, where he suffered a Fight of the Year contender loss to Poirier at UFC 281.

The latest UFC 303 lineup now includes:

• Michael Chandler vs. Conor McGregor
• Andre Fili vs. Cub Swanson
• Carlos Hernandez vs. Rei Tsuruya