Underground Kingz (UGK) was an American hip-hop duo from Port Arthur, Texas, formed in 1987 by Chad “Pimp C” Butler and Bernard “Bun B” Freeman. They released their first major album, Too Hard to Swallow, in 1992, followed by Super Tight in 1994 and Ridin’ Dirty in 1996. Both later albums charted on the Billboard 200 and received critical acclaim. The duo also appeared on major hits by other artists, including Jay-Z’s “Big Pimpin’” and Three 6 Mafia’s “Sippin’ on Some Syrup.”

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Pimp C was incarcerated in 2002 for an aggravated assault involving a firearm. During his imprisonment, Bun B kept the UGK name active, appearing on numerous tracks by other artists and consistently including messages such as “Free Pimp C!” Many artists in the Southern hip-hop community echoed these tributes in their own music. Pimp C was released in 2005.

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Rap-A-Lot Records released Pimp C’s solo debut, Sweet James Jones Stories, in 2005, featuring tracks recorded before his incarceration. That same year, Bun B released his solo debut Trill, which opened at number 6 on the Billboard 200 and reached number 1 on the Top R&B/Hip-Hop chart. After his release, Pimp C followed with his second solo album, Pimpalation.

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UGK’s self-titled album Underground Kingz debuted at number one on the Billboard 200 in August 2007. Guest artists included Talib Kweli, Too Short, Rick Ross, Z-Ro, Three 6 Mafia, Slim Thug, OutKast, Kool G Rap, and Big Daddy Kane, with production from Marley Marl. DJ Paul and Juicy J produced the album’s second single, “International Player’s Anthem (I Choose You).” The album received strong commercial success and critical praise, including a 4-star rating from AllMusic.

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On December 4, 2007, Pimp C died from an accidental combination of promethazine/codeine syrup and sleep apnea. In 2008, Bun B released his second solo album, II Trill. Its first single, “That’s Gangsta,” featuring Sean Kingston, debuted at number 2 on the Billboard 200, selling 98,000 copies in its first week. Other singles included “Damn I’m Cold” featuring Lil Wayne and “You’re Everything,” featuring Rick Ross, David Banner, DJ Corbett, and 8Ball & MJG—a tribute to Pimp C.

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Bun B’s third album, Trill OG, was released under Universal Music Group on August 3, 2010. In an interview with MTV Live, Bun B noted that the album included a previously unreleased verse by 2Pac.​ In Spring 2011, Bun B joined the faculty of Rice University as a Distinguished Lecturer, teaching a course in the School of Humanities focused on hip-hop and religion.