Josh Koscheck (born November 30, 1977) is an American retired mixed martial artist who fought in the Welterweight division of the Ultimate Fighting Championship (UFC) and Bellator MMA. Koscheck made his debut with the UFC on the first season of the reality television show The Ultimate Fighter as a middleweight, and had since fought for the company 25 times from 2005–2015, compiling a UFC record of 15–10 and having contended for the UFC Welterweight Championship once.

Prior to his MMA career, Koscheck was an accomplished wrestler at Waynesburg Central High School, graduating in 1997. He attended Edinboro University, where he won the 174-pound national championship in 2001 as a senior, and was a four-time NCAA Division 1 All-American collegiate wrestler.

Koscheck appeared on the first season of The Ultimate Fighter as a middleweight fighter. He defeated Chris Leben via unanimous decision to advance to the semifinals, where he was defeated by Diego Sanchez via split decision. Koscheck had his first official UFC fight on April 9, 2005, at The Ultimate Finale, where he defeated Chris Sanford with a first-round KO. Koscheck followed this victory with another win at UFC Ultimate Fight Night over Pete Spratt in Koscheck's debut at welterweight. Since then, Koscheck has amassed an additional three victories after experiencing his first career loss to Drew Fickett due to a rear naked choke. Koscheck then defeated Jonathan Goulet at UFC Fight Night 6 by submission due to strikes.

In 2006, Koscheck began training at the American Kickboxing Academy (AKA) in San Jose, California, to which he accredits his vastly improved kickboxing technique.

Koscheck's fight on December 13, 2006 was against Brazilian Jiu-Jitsu black belt Jeff Joslin at UFC Fight Night 7 where he won by unanimous decision.

Koscheck was then scheduled to fight Diego Sanchez on April 7, 2007 at UFC 69. This was the second encounter between the two Ultimate Fighter 1 alumni, now fighting as welterweights. The first fight – which did not count towards Koscheck's official record due to the bout being considered an exhibition match for The Ultimate Fighter television taping – resulted in a split decision win for Sanchez. At the weigh-ins for the event, Sanchez shoved Koscheck during the traditional post-weigh-in staredown. Although Sanchez continued to shout at Koscheck, no conflict ensued. In their fight, Koscheck defeated Sanchez by unanimous decision (30-27, 30-27, 30-27). Koscheck outstruck Sanchez throughout all three rounds and only shot in for a takedown once. During his post-fight interview, Koscheck repeatedly exclaimed, "Nineteen-and-one," in reference to Sanchez' first mixed martial arts defeat (including the two fights from The Ultimate Fighter show). UFC President Dana White announced a few weeks after the fight that Diego Sanchez had an undiagnosed illness before and during the fight which turned out to be a serious staph infection.

On August 25, 2007, Koscheck was defeated by Georges St-Pierre at UFC 74 via unanimous decision (30–27, 29–28, 29–28). St-Pierre's wrestling skills were displayed during the match by outwrestling Koscheck, scoring takedowns, stuffing Koscheck's takedown attempts and maintaining top position throughout most of the fight. There was speculation before the fight that Koscheck would outmatch St-Pierre on the ground due to his credentials, but St-Pierre was confident that he was a better wrestler and striker and was more well-versed in submissions than Koscheck.

Koscheck would rebound with a second round TKO victory over Dustin Hazelett at UFC 82.