Brazil Open Tournament

1997 saw Henderson make his debut in MMA, following in the footsteps of other wrestlers who were finding success in the sport. Henderson entered the Brazil Open Lightweight Tournament, which had a weight limit of 176 pounds, the lightest Henderson would ever compete at. It was a one-night tournament, featuring four competitors. After two relatively quick finishes, Henderson won the championship.

UFC 17

Less than one year later, Henderson entered his second MMA tournament, also a four-man tournament to be completed in one night. This time however, the weight limit was 199 pounds. UFC 17 would mark the start of Henderson's on-again off-again relationship with the UFC, which would span nearly two decades. He defeated Allan Goes and Carlos Newton in closely contested contests to earn his second MMA tournament championship. A punch delivered from Newton in their fight broke Henderson's jaw, but he continued fighting through it.

Rings: King Of Kings

About eighteen months later, Henderson entered his third MMA tournament. This time the number of competitors was 32, and there was no weight limit for any of the fighters. The tournament would be held over the course of two nights. The first two rounds were held in late 1999, while the final three were in early 2000. The tournament was full of many notable competitors, and Henderson faced Gilbert Yvel, Antônio Rodrigo Nogueira, and Renato Sobral. Despite weighing in at 199 pounds, and routinely being outweighed by more than 30 pounds, Henderson won all five of his fights, and became the Rings: King of Kings Tournament 1999 champion.

PRIDE Fighting Championships

This section needs expansion. You can help by adding to it. (November 2011)

Henderson began competing in Pride Fighting Championships in late 2000. He entered in three tournaments for the organization, winning the Welterweight (183 pounds) tournament at Pride Shockwave 2005 by defeating Murilo Bustamante by split decision. The opening two rounds of the eight-man tournament were fought at Pride Bushido 9, at which Henderson knocked out both Ryo Chonan and Akihiro Gono. Along with this tournament victory, he was awarded the Pride Welterweight Championship.

In 2006, Henderson lost a decision in a rematch against Kazuo Misaki. It was the first time in that he had lost a fight to an opponent who was under 205 pounds. Henderson's final Pride bout was a rematch with Wanderlei Silva at Pride 33 in Las Vegas, Nevada, on February 24, 2007, at which he scored a knockout victory to become Middleweight Champion (205 pounds), while still holding his Welterweight title. Henderson became the first fighter to hold titles in two different weight classes simultaneously in a major MMA organization.^[14] Overall, Henderson went 13–5 with Pride, with eight victories coming by stoppage.

UFC return

On September 8, 2007, Henderson returned to the UFC to face light heavyweight champion Quinton "Rampage" Jackson at UFC 75 in London, England. In a closely contested fight that saw Henderson impose his will early, Jackson controlled the later rounds and won a five-round unanimous decision to retain his title and gain the Pride middleweight title.

On November 17, 2007, it was announced during the post fight at UFC 78 that Henderson would fight UFC middleweight champion Anderson Silva to unify the Pride welterweight (183 lb) and UFC middleweight (185 lb) championships. UFC 82 took place on March 1, 2008, and was held at the Nationwide Arena in Columbus, Ohio. Despite winning the first round, Henderson lost via submission at 4:52 of the second round by rear naked choke.

Henderson bounced back from his inauspicious start in the UFC with a victory over Rousimar Palhares at UFC 88, winning by unanimous decision. After ten years in the sport, it was his first UFC victory. After the bout, Henderson laughed and said, "Hopefully I don't have to wait that long before I get my next win."

Henderson returned to the light heavyweight division to face former UFC Middleweight champion Rich Franklin on January 17, 2009, at UFC 93 in Dublin, Ireland. Henderson won the fight via a split decision following an eye-poke in the third round that many, including Franklin, thought was intentional. He was subsequently selected to lead Team U.S. on season 9 of The Ultimate Fighter, with Michael Bisping coaching the opposing Team UK.

Coaching The Ultimate Fighter and aftermath

The reality TV show, which spawned a feud between the two coaches that continued until their fight, aired on Spike TV and premiered on April 1, 2009, with the live finale on June 20, 2009, in Las Vegas.

On July 11, 2009, at UFC 100 at the Mandalay Bay Events Center in Las Vegas, Henderson and Bisping fought, culminating in Henderson becoming the first man to knock Bisping out, doing so in the second round with an overhand right to the jaw as Bisping was circling to Henderson's right. This win put Henderson back into contention for a title shot at the UFC Middleweight Champion. The knockout punch won Henderson a $100,000 bonus for "Knockout of the Night" and is considered one of the greatest knockouts in the history of the sport.

Controversy arose from the fight due to Henderson immediately following up his knockout punch with a flying forearm-drop to the undefended Bisping's head shortly before referee Mario Yamasaki ended the fight at 3:20.^[15]

Immediately after the fight, Henderson stated that "I hit him hard, but I got that last blow in just to shut him up a little bit." After UFC president Dana White said Henderson had made the comment in jest, Henderson clarified by stating, "When you're in the heat of the moment, the ref hadn't stopped me yet, who knows what's going to happen, if he's going to recover. I really only hit him twice, once on my feet, once on the ground. I didn't keep going. I didn't go after him after the ref tried to stop me, it was nothing like that. It was a reaction of mine to keep going until I was stopped—and you know, it did feel good though."^[16]

Strikeforce

Dan Henderson signed a four-fight, 16-month deal with Strikeforce on December 5, 2009, after his contract expired with the UFC. Henderson made his Strikeforce debut on April 17, 2010, at Strikeforce on CBS against Jake Shields.^[17] He was also eyed for a light heavyweight match against Gegard Mousasi,^[18] and expressed interest in eventually fighting Fedor Emelianenko at some point during his contract.^[19] Henderson lost his Strikeforce debut to Jake Shields. Despite hurting Shields and knocking him down in the 1st round, Henderson went on to lose by unanimous decision. The majority of the last rounds were spent on the ground where Shields controlled the fight via grappling. (49–46, 49–45, 48–45).

Henderson faced Renato Sobral on December 4, 2010, at Strikeforce: Henderson vs. Babalu.^[20] Henderson won the fight via KO at 1:53 of the first round.

Henderson defeated Rafael Cavalcante via third-round TKO for the Strikeforce Light Heavyweight Championship at Strikeforce 32. After two rounds in which all three judges had the score tied 19–19, Henderson dropped Cavalcante with his famed right hand in the third before referee Dan Miragliotta called the fight off at the 0:50 mark.

Henderson fought Fedor Emelianenko on July 30, 2011, at Strikeforce: Fedor vs. Henderson.^[21][22] Many had speculated that Henderson would meet Fedor at a catch weight, but Strikeforce later confirmed the fight as a heavyweight bout. Henderson said, "Its tough for me to gain weight. I did weightlifting and plenty of eating; I don't know what else I'm supposed to do. I'm not going to feel outmatched or small in there."^[23] He had to step on the scales weighing at least 206 pounds in order to qualify for the heavyweight division, and weighed in at 207. Fedor weighed in a bit below his normal weight, with the scale reading 223 pounds.^[24] Henderson defeated Emelianenko via KO^[25][26][27] at 4:12 of the 1st round. This was the last fight on Henderson's Strikeforce contract. Henderson said he would like to re-sign to defend his Strikeforce Light Heavyweight Championship.

Third UFC run

Shortly after the UFC 133 pre-fight press conference, Dana White commented on the potential to bring Henderson back to the UFC for a third go-around. "We'll see what happens," White said on Thursday in Philadelphia. "'Hendo and I have had some history in dealing. We'll see if we can figure something out and get him back in the UFC."^[28] Later Henderson commented, "I think the biggest fight they could promote is probably a title unification with whoever is the champ in the UFC."^[29]

Henderson faced Maurício Rua on November 19, 2011, at UFC 139 for his third run in the UFC.^[30] He won the bout via unanimous decision. The back and forth action earned both fighters Fight of the Night honors, and was described by many as one of the greatest fights in UFC history.^[31][32]

UFC President Dana White announced during the post-fight press conference of UFC 145 that Henderson would be the next opponent for Light Heavyweight Champion Jon Jones.^[33]

The bout with Jones was expected to take place on September 1, 2012, at UFC 151.^[34] However, Henderson withdrew from the fight citing a knee injury, and the remainder of the fight card was cancelled.^[35]

Henderson faced Lyoto Machida on February 23, 2013, at UFC 157.^[36] He lost the bout via split decision.

Henderson faced Rashad Evans on June 15, 2013, in the main event at UFC 161.^[37] He lost via split decision.

Henderson faced Vitor Belfort in a rematch on November 9, 2013, at UFC Fight Night 32.^[38] Henderson defeated Belfort in their first encounter in 2006 at Pride 32 via unanimous decision. He lost the fight via knockout in the first round, marking the first time in his MMA career that he had been stopped due to strikes. The match with Belfort was the last fight of Henderson's contract with UFC. On January 22, Henderson revealed to UFC Tonight that he signed a new, six-fight contract with the UFC.^[39]

In January 2014, a rematch with Maurício Rua was announced to take place on March 23, 2014, at UFC Fight Night 38.^[40] Despite losing the first two rounds after being knocked down by Rua, Henderson rallied back in the third round and won the fight via TKO due to punches. The win also earned Henderson his third Fight of the Night bonus and first Performance of the Night bonus.^[41]

Making a quick return to the cage, Henderson faced a much larger Daniel Cormier on May 24, 2014, at UFC 173.^[42] He lost the fight via submission (technical submission/rear-naked choke) in the third round after being out-wrestled and held down on the bottom for the majority of the fight.^[43]

On November 12, 2014, the UFC announced that Henderson would move down to Middleweight to face Gegard Mousasi on January 24, 2015, in the co-main event at UFC on Fox 14.^[44] He lost the fight via TKO in the first round.^[45]

Henderson faced Tim Boetsch on June 6, 2015, in the main event at UFC Fight Night 68.^[46] He won the fight via knockout at 28 seconds of the first round.^[47]

Henderson faced Vitor Belfort in a rubber match in the main event at UFC Fight Night 77.^[48] He again lost the bout via a combination of head kick and punches.^[49]

A rematch with Lyoto Machida was expected to take place at Middleweight on April 16, 2016, at UFC on Fox 19.^[50] However, on April 13, the UFC announced that Machida declared the usage of a banned substance during an out-of-competition sample collection last week. Machida stated that he was unaware that the substance was prohibited both in and out of competition. Therefore, he was removed from the bout and Henderson was re-booked for another event at a later date.^[51]

Henderson was quickly rescheduled to face Héctor Lombard on June 4, 2016, at UFC 199.^[52] He won the fight via knockout in the second round via a head kick followed by a reverse elbow and earned himself a Performance of the Night bonus, as well as becoming the first fighter to knock Lombard out cold.^[53][54]

Henderson faced then UFC Middleweight Champion Michael Bisping, in a rematch on October 8, 2016, at UFC 204.^[55] Despite dropping and nearly finishing Bisping in both the first and second round, he wound up losing the back and forth fight via unanimous decision.^[56] Both fighters were awarded Fight of the Night for their performance.^[57] At the conclusion of the fight, Henderson confirmed his intention to retire from fighting.^[58]

Dan Henderson was inducted into the Fight Wing of the UFC Hall of Fame at the UFC Fan Expo on July 5, 2018, alongside Maurício Rua, for their fight in 2011.^[59]