UFC 84: Ill Will was a mixed martial arts event held by the Ultimate Fighting Championship (UFC) on May 24, 2008, at the MGM Grand Garden Arena in Las Vegas, Nevada.

The card featured the return of Sean Sherk, who was suspended and stripped of his UFC lightweight title after he tested positive for steroids at UFC 73. He faced B.J. Penn, who had since won the vacated title against Joe Stevenson at UFC 80. This event also marked the last appearance of Tito Ortiz in the UFC for well over a year, as he was at the end of his contract and due to his feud with Dana White was not expected to re-sign at the time.

This event also marked the UFC debut of future UFC Interim Heavyweight Champion Shane Carwin.

This event was awarded Sherdog's 2008 Event of the Year.

At the end of this event, the UFC awarded $75,000 to each of the fighters who received one of these three awards.

B.J. Penn ($250,000) def. Sean Sherk ($35,000)

Wanderlei Silva ($150,000) def. Keith Jardine ($10,000)

Lyoto Machida ($100,000) def. Tito Ortiz ($210,000)

Jacob Christopher "Tito" Ortiz (English: /tɪtɵ ɔərtɪs/) (born January 23, 1975) is an American mixed martial artist and former UFC Light Heavyweight Champion, having held the title from April 14, 2000 to September 26, 2003. Along with fighters like Randy Couture and Chuck Liddell, he was one of the sport's early stars. Ortiz ultimately became the biggest pay-per-view draw of 2006 for his fights with Liddell, Forrest Griffin, and Ken Shamrock.

Outside of his fighting career, Ortiz is the CEO of the Punishment Athletics MMA equipment and clothing line. He also owns an MMA training gym called Punishment Training Center, which is located in Huntington Beach, CA.

Jacob Christopher Ortiz was born to Samuel and Joyce Ortiz. He received his nickname "Tito," which means tyrant, from his father when he was a year old. He is the fourth child of his mother, Joyce, who had three sons from a previous marriage. His mixed heritage (Mexican father, American mother) has been reflected in his ring entrances as he has borne both Mexican and American flags.

Lyoto Carvalho Machida (Portuguese pronunciation: [liˈotu maˈʃidɐ]; born May 30, 1978) is a Japanese-Brazilian mixed martial artist from Salvador, Bahia, Brazil who fights as a light heavyweight in the Ultimate Fighting Championship. He is a former UFC Light Heavyweight Champion and is currently ranked as the #6 light heavyweight fighter in the world by Sherdog, MMAWeekly and Yahoo! Sports.

Machida was born in the city of Salvador as the third son of the highly ranked head of the Brazilian branch of the Japan Karate Association, Shotokan karate master Yoshizo Machida. Yoshizo moved to Brazil from Japan when he was 22 years old. There he met and married Lyoto's mother, Ana Claudia. Growing up in Belém, Lyoto began training in karate at the age of three and earned his black belt at the age of thirteen. He also began training in sumo at twelve and Brazilian Jiu-Jitsu at fifteen. He won a number of amateur karate tournaments, including the 2001 Pan American Karate tournament.

He was the runner-up in the 2000 Brazilian Sumo Championships in the 115 kg division. As an adult, he became Brazilian Champion twice under Taylor Swanson, and placed second in the South American Championship. He defeated American black belt Jiu-Jitsu fighter Rafael Lovato Jr. at L.A. Sub X. In addition to his sumo and karate achievements, he has a college degree in Physical Education. Lyoto's brother, Chinzô, is a Shotokan vice-champion (Australia 2006), losing only to number-one ranked Shotokan master Koji Ogata. Lyoto and Chinzô fought in a Karate Final 10 years ago in which Lyoto gave Chinzô a cheek scar that still exists today. His other brothers include Kenzo Machida, a TV journalist for one of Brazil's biggest TV stations, Take Machida and adopted brother Francisco Machida.

Wanderlei César da Silva ( /ˈvændərleɪ/ VAN-dər-lay; Portuguese: [vɐ̃dɛɾˈlej ˈsɛzɐr dɐ ˈsiɫvɐ];Japanese: [ba̠nda̠ɽe̞i ɕiü͍βa̠]; born July 3, 1976), nicknamed "The Axe Murderer", is a Brazilian mixed martial artist, who has competed in Japan's Pride Fighting Championships and the American based Ultimate Fighting Championship (UFC). Silva is known for his aggressive fighting style with the majority of his fights ending in knockout or referee stoppage due to strikes. His style includes engaging opponents with punches and knees from the Muay Thai clinch. He holds the record for the most wins and knockouts in Pride FC history. He is currently ranked as #22 best middleweight fighter in the world by FightMatrix.com.

Silva began his training under Rudimar Fedrigo at the Chute Boxe Academy in his hometown of Curitiba, Brazil. Although he specializes in muay Thai, he has also trained and received his black belt in Brazilian jiu-jitsu from trainer Cristiano Marcello. Silva was given the nickname "Cachorro Louco" ("Mad Dog") in Brazil because of his aggressive style and his pre-fight opponent "stare down". He is the former IVC Light heavyweight Champion, former PRIDE Middleweight Champion, and the 2003 PRIDE Middleweight Grand Prix Tournament Winner.

Keith Hector Jardine (born October 31, 1975) is an American mixed martial artist who competes in the Middleweight division and is best known for his time in the Ultimate Fighting Championship, where he fought in the Light Heavyweight division. During his time in the Ultimate Fighting Championship, he held notable wins over Forrest Griffin, Chuck Liddell, and Brandon Vera. In 2011, Jardine signed a multi-fight deal with Strikeforce.

Jardine made his professional Mixed Martial Arts debut in 2001, defeating Amir Rahnavardi by armbar submission. He would win five out of his next six bouts, suffering one knockout loss to Travis Wiuff six second into the fight, before debuting in the Japanese Pancrase organization in 2003. Jardine's bout in Pancrase, with Keiichiro Yamamiya, ended in a draw. Jardine defeated his next two opponents, including a submission win over Red Devil Sport Club fighter Arman Gambaryan, before appearing on The Ultimate Fighter 2.

In 2005, Jardine was cast on the second season of The Ultimate Fighter, a team-based reality television show created by the UFC, as a heavyweight competitor. He was the first heavyweight to be chosen by team coach and then UFC middleweight champion Rich Franklin. Although considered a favorite to proceed to the heavyweight division's finals, Jardine was not selected to fight until the semi-finals, where he was defeated by eventual heavyweight winner and his future sparring partner, Rashad Evans.