Alistair Overeem was too much for Brock Lesnar in the main event as the Dutch kickboxer dominated to a first round stoppage.

Unable to secure an early takedown, Lesnar was muscled into a clinch by Overeem who began blasting away with knees. As more strikes landed to Lesnar's core, the former UFC heavyweight champion began to fade.

Lesnar was unable to land any significant strikes on the feet and a leg kick from Overeem was enough to send Lesnar to the canvas. A few bombs from Overeem's right hand to his grounded opponent were enough to secure a TKO victory 2:36 into the first round. With the defeat, Lesnar also announced his retirement.

"My hat is off to Alistair Overeem...I'm going to officially say that tonight is the last night you will see me in the Octagon. Brock Lesnar is officially retired. I promised my wife and my kids if I won this fight that I would get a title shot and that would be my last one, but if I lost tonight, I'd retire. Everyone, you've been great" Lesnar said shortly after his bout in the post fight interview.

Overeem now becomes the top contender and will challenge current heavyweight champion Junior dos Santos for his title in a future event.

In the co-main event, a lightweight tilt between Donald Cerrone and Nate Diaz ended with Diaz handily winning the matchup. Diaz took over the fight with consistent punch combinations, mixing head and body that left Cerrone blooded at the fight's end.

Diaz won via unanimous decision and extends his win streak to two fights, improving his record to 15-7.

Cerrone, who was on the verge of being a lightweight contender, has his six fight win streak snapped with his loss to Diaz and falls to 17-4 and one no contest.

Also on the main card were welterweights Jon Fitch fighting Johny Hendricks. Despite being an underdog, Hendricks took care of business rather quickly. Just 12 seconds into the bout, Hendricks fired a blistering left hook that sent Fitch limp to the canvas.

Hendricks improves to a three fight win streak, 12-1 overall.

Fitch suffers his first stoppage since 2002. The loss is sure to set back the AKA member who Dana White recently announced was back in the mix for welterweight title contention had he won against Hendricks. Fitch drops to 23-4-1 and one no contest.

Alexander Gustafsson vs. Vladimir Matyushenko featured another knockout on the main card. Gustafsson felled Matyushenko with a perfectly placed left jab just as "The Janitor" was charging in. Gustafsson followed up with unanswered hammer fists to Matyushenko and secured his TKO victory at the 2:35 mark.

Gustafsson improves to 13-1, four fight win streak, and Matyushenko falls to 26-6.

Lastly, Jim Hettes took on TUF veteran, Nam Phan, in a featherweight bout. Hettes defeated another TUF 11 cast member, submitting Alex Caceres in his last bout, as he dominated Phan from the opening bell. From striking on the feet to grappling on the ground, easily gaining full mount on a few occasions, the fight was all Hettis' as he wins via unanimous decision.

Hettis stays undefeated at 10-0.

Phan drops to 17-10.