Nicholas Robert Diaz[3] (born August 2, 1983) is an American professional boxer[4] and mixed martial artist who competes in the Welterweight and Middleweight divisions of the Ultimate Fighting Championship (UFC).

[12][13] Diaz began training in karate and aikido from a young age and also participated in wrestling tournaments during his teenage years.

[13] Prior to his debut professional mixed martial arts fight, Diaz's girlfriend, Stephanie died by suicide by walking in front of traffic.

[18] Diaz became a professional mixed martial arts fighter in 2001 just after his 18th birthday and won his first fight, submitting Mike Wick with a triangle choke at IFC Warriors Challenge 15.

[27] Diaz returned to the Octagon at UFC 47, set to take on future EliteXC Middleweight Champion Robbie Lawler.

[30] Diaz was confident coming into the bout but was unable to achieve success in the match, ultimately losing to Sanchez by unanimous decision.

[citation needed] Riggs prevailed in a hard-fought battle, winning by unanimous decision and giving Diaz his second straight loss.

[34] Diaz returned to his hometown of Stockton and participated in the International Cage Fighting Organization's inaugural event, defeating Ray Steinbeiss by unanimous decision.

[citation needed] After Alessio pulled out, Diaz took advantage of the opportunity, submitting veteran Josh Neer in the third round.

[39] GFC had Diaz scheduled to fight Thomas Denny in January 2007, but due to poor ticket sales the event was ultimately scrapped.

[40] At the end of the first round, apparently due to poor cardio on Gomi's part, the Japanese fighter was clearly stunned, throwing much wilder punches and barely maintaining his defense.

[45] MMA Weekly reported that Nick Diaz signed a two-year deal with EliteXC and in his next fight, fought K. J. Noons for the vacant 160 pound title.

[46][47] After losing to Noons, Diaz had surgery and had the bone filed down on his eyebrows to mitigate any bad cuts in future bouts.

Diaz came into his next fight at EliteXC's "Return of the KING" event in Honolulu, Hawaii against Muhsin Corbbrey 9 pounds over the weight limit.

[48] Diaz earned a tough win over Corbbrey, following the main event an altercation between Nick and his brother Nate broke out with K. J. Noons and his corner.

"[53] Diaz was scheduled to face Eddie Alvarez for the EliteXC 160 pound title on November 8, 2008 before the company ceased operations.

[57] Throughout the fight, Diaz was dominant in all areas using effective positioning on the ground, once mounting Frank in the end of the first round, before finally finishing the fight in the second round with a body shot that crumpled Frank to the mat and follow up punches before referee John McCarthy called a halt to the bout.

The two men continued to exchange, with Diaz utilizing his unorthodox boxing skills, until rocked by a Žaromskis left hook and falling to his back.

In the few remaining minutes, Diaz opened up with his boxing range, tagging Žaromskis cleanly several times with combos composed of jabs, hooks and seamless bodyshots; forcing him against the side of the cage where he landed a solid uppercut that dropped his opponent leading to the referee to stop the contest at 4:38 of the first round.

White later confirmed via Twitter that Diaz would face St-Pierre at UFC 137 at the Mandalay Bay Event Center in Las Vegas, Nevada, on October 29, 2011.

[80] Diaz called out St-Pierre in the post-fight interview,[81] who was scheduled to fight Condit at the same event but had been forced out of the bout with a knee injury.

[83] However, due to an ACL injury sustained by St-Pierre, Diaz faced Carlos Condit in the main event, with the winner being awarded an Interim UFC Welterweight Championship.

[89] The Nevada State Athletic Commission temporarily suspended Diaz shortly after the positive test, pending a full disciplinary hearing.

[90] It was announced at the hearing in May 2012 that Diaz was suspended for one year, retroactive to February 4, 2012, and fined 30 percent of his fight purse earned from the Condit bout.

The commission rejected the defense and suspended him for one year retroactive to the date of the fight, as the current guidelines were not in effect at the time of the failed tests.

On September 14, 2015 the Nevada State Athletic Commission suspended Diaz for 5 years and fined him $165,000 following his failed drug test of marijuana metabolites at UFC 183.

[103] Diaz, according to sources, has reached an agreement with the Nevada Athletic Commission, which now frees him to participate in all combat sport-related activities in the state once again.

[120][121] In 2023, Diaz starred in the film Darkness of Man with Jean-Claude Van Damme, directed by James Cullen Bressack.

[123] The first event took place on June 22, 2013 in Stockton, California, headlined by Diaz's teammate Daniel Roberts against Justin Baesman.

[128] After UFC 158, Estima, who was a training partner for Georges St-Pierre, attempted to shake Diaz's hand immediately after the fight.