Charles David Liddell (born December 17, 1969) is an American former professional mixed martial artist. A professional competitor from 1998 to 2018, Liddell is a former UFC Light Heavyweight Champion (from 2005 to 2007) and is widely credited, along with fellow UFC fighter Randy Couture, with helping bring MMA into the mainstream of American sports and entertainment. Known as "The Iceman", Liddell achieved a 16–7 MMA record in the UFC, and an overall MMA record of 21–9, with 13 of his wins coming by way of knockout. He also achieved a 20-2 record in kickboxing, with 16 of his wins coming by way of knockout, and won two national amateur championships. He retired in late 2010, then came out of retirement for one bout in 2018, in a loss to rival Tito Ortiz. On July 10, 2009, Liddell was inducted into the UFC Hall of Fame.

Born in Santa Barbara, California, Liddell was raised by his single mother and maternal grandfather, who taught Liddell and his siblings boxing techniques from a very young age. Liddell began studying Karate at the age of 12; the tattoo on his scalp reads "Koei-Kan" (幸栄館).

While growing up in Santa Barbara, he often frequented the Del Playa Drive, a street popular for parties in the UCSB college town of Isla Vista. As Liddell wrote in his book Iceman: My Fighting Life, he often found himself in fights with drunk college students older than him.

In high school, Liddell was a four-year starter on the football team at San Marcos High School, playing center and linebacker, and he also excelled at wrestling. In college, he wrestled at Cal Poly, where he attended from 1988 to 1993, and graduated with a bachelor's degree in business/accounting in 1995. Liddell was inducted into the Cal Poly Hall of Fame in 2009.

Lidell competed as an amateur in both folkstyle wrestling and kickboxing. He wrestled for Cal Poly from 1988 to 1993 and compiled an amateur kickboxing record of 20 wins (16 KOs) and 2 losses (becoming a two-time national amateur champion) before transitioning to mixed martial arts.

Liddell made his UFC debut in 1998 during UFC 17 in Mobile, Alabama with a decision victory over Noe Hernandez. In his next bout, he faced Brazilian fighter Jose "Pele" Landi-Johns at an International Vale Tudo Championship event in São Paulo, Brazil, which was bare-knuckle. Despite being a heavy underdog in his opponent's home country, Liddell dominated the vale tudo fighter on the feet, and won via decision. After a technical submission loss to top contender Jeremy Horn shortly after, Liddell began establishing his reputation as a top contender with dominant victories over Kevin Randleman, Murilo Bustamante, Vitor Belfort, Amar Suloev, Jeff Monson, and Renato Sobral. Liddell was also the first UFC fighter to fight in Pride, where he represented the organization against fellow kickboxer Guy Mezger, knocking him unconscious.

By 2002, Liddell was considered the #1 contender for the UFC Light Heavyweight Championship, with growing popularity and support from his fans. The UFC tried to arrange a title bout with then-champion Tito Ortiz, but Ortiz cited scheduling conflicts.

To force Ortiz's hand, they created an interim light heavyweight championship and matched Liddell with Greco-Roman wrestler and former heavyweight champion "The Natural" Randy Couture at UFC 43. Couture neutralized Liddell's hooks with straight punches and eventually began taking "The Iceman" down at will. Couture eventually gained full mount and forced a referee stoppage due to a barrage of punches.