Nathan Joel Marquardt (born April 20, 1979) is an American mixed martial artist who competed in the middleweight and welterweight division of the Ultimate Fighting Championship.

Marquardt's late father was a Lutheran pastor, worked in construction, and was also a Marine veteran who fought in the Vietnam War.

When he was 15 years old, he began studying the disciplines of Wing Chun Kung Fu, Japanese Jujutsu, Freestyle Wrestling, and Kenpo Karate.

Marquardt was active in other sports as well, including basketball and soccer, at Wheat Ridge High School and also began taking Kickboxing and Brazilian Jiu-Jitsu lessons when he was 18 years old under the instruction of Ricardo Murgel.

A final encounter between the two fighters in December 2002 saw Marquardt defeat Kunioku once again to recapture the King of Pancrase championship, which he held for nearly a year.

After he was freed, Marquardt threw a strike at Almeida's face, prompting both corners to storm into the ring, including Renzo Gracie.

After Almeida vacated his title in July 2004, Marquardt proceeded to regain the championship in a victory over Kazuo Misaki at Pancrase: Brave 10.

On May 1, 2005, Marquardt defeated Izuru Takeuchi, winning the Pancrase Middleweight Championship for the seventh time, becoming the only fighter to ever accomplish such a feat.

Although Marquardt earned a unanimous decision victory over UFC veteran Ivan Salaverry, a post-fight drug test revealed high levels of nandrolone, an anabolic steroid, in Marquardt's system which led to the Nevada State Athletic Commission filing for his suspension.

[17] With the drug testing controversy resolved, Marquardt was set to make his return at UFC 58, against veteran Joe Doerksen.

In the post-fight interview, Marquardt stated his goals of capturing the UFC Middleweight Championship and his intention to fight then-champion Rich Franklin.

After early speculation that Marquardt's contract with the UFC could expire without renewal,[20] he confirmed that a new agreement had been signed with the organization.

Nate defeated Kampmann in 82 seconds by throwing a head kick and landing a barrage of strikes to take the win by TKO in the first round.

Marquardt obtained a second straight win to launch himself back into the title picture at UFC 95, when he defeated well-regarded Brazilian fighter Wilson Gouveia with another barrage of strikes to earn a third-round TKO.

Following his victory over Maia, Marquardt was scheduled to fight Dan Henderson to determine number one contendership to Silva's Middleweight Championship.

Although able to lock in a guillotine choke late in the third round, Marquardt was not able to finish the submission attempt and lost the fight in an upset via unanimous decision.

UFC broadcaster Joe Rogan immediately announced that Marquardt had passed an inspection from the ringside physician and the referee.

Less than a week after his win over Palhares, Marquardt was tapped to make a quick return to the Octagon to face Yushin Okami in a middleweight title eliminator bout on November 13, 2010 at UFC 122, replacing Vitor Belfort,[30] as Vitor was promoted to a title fight because of Chael Sonnen's suspension for PEDs.

After defeating Miller, Nate's teammate, Georges St-Pierre, gave him the idea of dropping down to the welterweight division.

[37] According to a video posted by Dana White on his Twitter, Marquardt was released by the UFC due to failing "medical requirements".

On June 28, 2011, Nate appeared on MMA Hour with Ariel Helwani and stated that in August 2010 he felt tired and moody and his doctor discovered he had low testosterone levels.

At the end of that period, both the specialist and Nate's primary doctor agreed his levels really were low and he was a candidate for replacement therapy.

Nate's primary doctor injected him with testosterone to quickly get his levels back up in time for his scheduled fight against Story.

Nate claimed that he retook tests on the day of the fight and was actually within qualifying limits, thus having his suspension lifted by the commission.

[38] Shortly after having his suspension lifted by the Pennsylvania State Athletic Commission, Marquardt signed with top U.K. fight promotion BAMMA, the British Association of Mixed Martial Arts.

Marquardt made a return to the middleweight division to face James Te-Huna on June 28, 2014 at UFC Fight Night 43.

[53] Marquardt won the fight via knockout in the second round and was awarded a Performance of the Night bonus.