Joseph Jonathan "Diesel" Riggs (born September 23, 1982) is an American mixed martial arts fighter. He has competed at weights ranging from Heavyweight down to Welterweight. Currently, Riggs fights as a Welterweight.

Riggs started boxing as a child with his father. Although Riggs is right handed, he was encouraged by his boxing coach to fight southpaw, making his power hand his lead hand. He used to be a boxer.

He began wrestling at Cactus high school in Glendale, AZ he followed in the footsteps of his hero, Randy Couture, and became an All-American twice. Currently, Riggs also holds a blue belt in Brazilian jiu-jitsu under Second-Dan BJJ black belt, Gustavo Dantas. His manager and trainer is Scott Lewis. Riggs has also trained at Arizona Combat Sports under the Lally brothers.

Riggs' strength training consists primarily of plyometrics. His weight training is geared to maintain his muscle mass, and consists of squats, deadlifts and cleans. Riggs does a lot of pushups and circuit training.

Riggs credits his success to his knockout power and athleticism. He says that his favorite technique is a right hook, which he knocked out Luke Stewart with on November 20, 2008. Riggs has fought in the UFC eight times, and has also appeared at the Playboy Mansion twice fighting under the Strikeforce banner.

Over his career, Riggs has fought in the Heavyweight, Light Heavyweight, Middleweight and Welterweight divisions, and became a four-time Desert Quest champion, two-time Grappler's Quest Advance champion, Rage in the Cage Heavyweight and Middleweight champion, Art of War Heavyweight champion, Evolution Combat Heavyweight champion, and XCF Light Heavyweight champion.

Riggs' dream of fighting in the UFC materialized in 2004, in a winning bout against Canadian fighter Joe Doerksen. Riggs received his shot at the UFC Welterweight title at UFC 56 in November 2005 against Matt Hughes.

Originally, the title shot was offered to Karo Parisyan, who had to withdraw due to a torn hamstring. When Riggs was contacted to take Parisyan's place he jumped at the chance, despite having fought at UFC 55 just a month earlier. However, Riggs did not make the required weight and the fight was declared a non-title event, due to Hughes allowing Riggs to fight him (if a fighter does not make weight for a match, the match may still take place if their opponent allows it). Despite his efforts, Riggs could not mount a significant challenge; Hughes took him down and submitted him with a kimura from half-guard just minutes into the first round of the fight.

Following his loss to Hughes, Riggs rebounded to win against Nick Diaz (decision) at UFC 57. In the hospital room after the fight, Diaz and Riggs got into a physical altercation where they had to be separated by police.

Riggs then moved up to Middleweight to face The Ultimate Fighter alumni Mike Swick. Early in the fight Riggs was caught in a guillotine choke and tapped out. Riggs then fought The Ultimate Fighter 2's Jason Von Flue, submitting him with a triangle choke.

Riggs' last UFC bout was on December 13, 2006 against Welterweight contender Diego Sanchez at UFC Fight Night 7. Riggs lost the fight due to knockout from a hook followed by a knee in 1:45 of the first round.

Following the fight with Sanchez, Riggs chose to go to the WEC and compete for the vacant Middleweight championship, but had to pull out of the fight the day before because of a recurring back injury.

Most recently, Riggs lost to Cory Devela via TKO at Strikeforce: At The Dome due to re-injuring his back while pummeling before Devela threw him. He was a heavy favorite in this fight, and his loss continued a streak of performances that did not live up to the expectations for the talented fighter (particularly vs. Hughes, Salaverry, Swick, and Sanchez).

Riggs was to return to action on Strikeforce: Melendez vs. Thomson, facing Jiujitsu specialist Luke Stewart. Riggs stepped in as a late replacement for Shonie Carter who was injured in training. The fight was to be contested at a catchweight of 178 pounds. However, He was denied licensure by the California State Athletic Commission after disclosing his recent use of prescription medication during the licensing process.

Joe Riggs lost to Kazuo Misaki at Strikeforce at the Playboy Mansion on Semptember 20, 2008. Joe Riggs won his last fight at Strikeforce: Destruction on November 21, 2008 against Luke Stewart by TKO (Punches) in 2nd round 2:05. Riggs broke his hand throwing the first punch of the bout, but managed to rally in the second round, breaking Stewart's nose in the process.