UFC Welterweight Champion Georges “Rush” St. Pierre will face Strikeforce Welterweight Champion Nick Diaz at UFC 137. UFC President Dana White announced the matchup this afternoon, and it will reportedly take place on October 29th at the Mandalay Bay Events Center in Las Vegas, Nevada.

St. Pierre has won nine straight fights inside the Octagon and some feel that he has cleaned out the UFC’s welterweight division. Diaz, meanwhile, has won ten straight and has reigned supreme atop the Strikeforce 170-pound division since winning the promotion’s title on January 30, 2010.

St. Pierre (22-2-0), despite recently developing a reputation for “fighting safe,” has handily defeated all challengers to his title since reclaiming the belt at UFC 83 over three years ago. Of his six most recent title defences, only one has ended inside the distance; a UFC 94 rematch with former two-division UFC champion B.J. Penn that was stopped after the fourth round. St. Pierre has been dominant in each defence of his title, however, though an eye injury appeared to hamper him in his bout with former Strikeforce Middleweight Champion Jake Shields in April.

Diaz (25-7-0, 1 ND), in stark contrast to St. Pierre, has finished nearly all of his recent opponents and has developed a “love him or hate him” reputation for his brash comments. The Stockton, California native defeated DREAM champion Marius Zaromskis to become the inaugural Strikeforce Welterweight Champion in 2010 and has since defended the title three times. Most recently, Diaz knocked out UFC and Cage Rage veteran Paul “Semtex” Daley late in the first round of their April 9th title bout.

Details of the St. Pierre-Diaz matchup are limited and it is currently unclear whether Diaz’s Strikeforce title will be on the line as well as St. Pierre’s. USA Today reports that Diaz has signed an eight-fight deal with Zuffa that will allow him to compete for both the UFC and Strikeforce. He will not be permitted to box, as he has recently expressed interest in doing.

While not yet officially announced by the promotion, UFC 137 is expected to take place on October 29th at the Mandalay Bay Events Center in Las Vegas, Nevada. The event will mark the first time that Diaz has competed inside the Octagon since a UFC 65 victory on November 18, 2006.

(Photo Credit: Sherdog.com)