Kamarudeen Usman (born May 11, 1987) is a Nigerian-American professional mixed martial artist, former freestyle wrestler, and graduated folkstyle wrestler. He currently competes in the Welterweight division of the Ultimate Fighting Championship (UFC), where he is a former UFC Welterweight Champion. Usman is also The Ultimate Fighter 21 tournament winner. He is considered one of the greatest Welterweights of all time. As of November 18, 2025, he is #8 in the UFC welterweight rankings.

As a freestyle wrestler, Usman primarily competed at 84 kilograms (185 lb), and was a 2010 U.S. University World Team Member. Collegiately, he competed at 174 pounds (79 kg), and was the 2010 NCAA Division II national champion, a three–time NCAA Division II All-American, and a NAIA national qualifier.

Usman was born in Auchi, Edo state of Nigeria. His father was a major in the Nigerian Army and his mother was a teacher. Usman had a modest upbringing during his childhood. Usman's father Muhammed Nasiru Usman, who became a pharmacist in the United States, brought his family into the country when Usman was eight years old, immigrating to Dallas, Texas. He has two brothers, Kashetu and Mohammed, the latter of whom is also a mixed martial artist and fellow The Ultimate Fighter (TUF) winner.

Usman started wrestling in his sophomore year at Bowie High School in Arlington, Texas. Because Usman's wrestling coach at the time had trouble pronouncing his first name Kamarudeen, he got the nickname "Marty" when he joined the team and it stuck with him during his amateur wrestling career. After compiling a 53–3 record as a senior and placing third at the Texas state championships, Usman wrestled at the senior national tournament before leaving for college.

In college, Usman wrestled in Iowa at William Penn University for one year, where he was an NAIA national tournament qualifier in 2007, but was unable to attend the tournament due to a snowstorm; half of his team and his head coach, however, left early for the tournament without him, which frustrated Usman and influenced him to leave William Penn. He later transferred to the University of Nebraska at Kearney (UNK), which previously tried to recruit him under advisement of then-UNK wrestler Tervel Dlagnev, and subsequently helped the Lopers win their first-ever team title in 2008. Usman placed top three in the nation all three years he attended UNK and was a two-time national finalist. He became the NCAA Division II national champion at 174 pounds in 2010, finishing the season with a 44–1 record and 30 straight wins.

Shortly after his folkstyle career was over, Usman turned his attention to freestyle wrestling and became a resident of the United States Olympic Training Center, with hopes of making the 2012 Olympic team. Despite making the U.S. University World Team in 2010, Usman was sidetracked by injuries and eventually abandoned his Olympic goal after failing to qualify for the 2012 U.S. Olympic Team Trials, turning his attention to mixed martial arts instead. Former National Football League (NFL) star Christian Okoye, who has the nickname "The Nigerian Nightmare" trademarked, gave his blessing for Usman to use it.

In 2011, Usman served as the wrestling coach for Team Miller in The Ultimate Fighter season fourteen. After failing to qualify for the 2012 US Olympic Team Trials in freestyle wrestling, Usman made his professional MMA debut in November 2012. He compiled a record of 5–1, competing for several regional promotions before trying out for The Ultimate Fighter in early 2015.

In February 2015, it was announced that Usman was one of the fighters selected to be on The Ultimate Fighter 21.