Def Jam Recordings, commonly referred to as Def Jam Records or just Def Jam, is a United States based hip-hop record label, owned by Universal Music Group, and operates as a part of The Island Def Jam Music Group.
Def Jam was founded by Rick Rubin in his dorm room at New York University. Russell Simmons joined Rubin shortly after when they were introduced to each other by Vincent Gallo. The first releases on Def Jam Recordings were LL Cool J,' “I Need A Beat,” and the Beastie Boys,' “Rock Hard,” both in 1984. The singles sold well, eventually leading to a distribution deal with CBS Records' (which would later become Sony Music Entertainment) Columbia Records the following year. The first full-length album released by Def Jam Recordings was LL Cool J’s Radio in December of 1985. The following year, Def Jam created a short-lived subsidiary label called OBR Records, catered toward R&B artists—the first artist signed to that imprint was Oran "Juice" Jones, who enjoyed success with his hit single “The Rain.” Def Jam also signed thrash metal band Slayer. As the decade drew to a close, the label signed Public Enemy, whose controversial lyrical content garnered the company both critical acclaim and disdain.
Lyor Cohen became president of Def Jam in 1988, after winning a power struggle with Rubin, who would shortly thereafter leave the company to form Def American Recordings (now known as American Recordings).
Def Jam under PolyGram
In the early 1990s, the company created “Rush Associated Labels”, a larger moniker under which Def Jam and its various auxiliary labels would operate as subsidiaries. By 1992, despite recent multi-platinum selling releases from LL Cool J., Public Enemy, and EPMD, Def Jam ran into severe financial troubles and was faced with folding. Salvation came in 1994, however, when PolyGram purchased Sony’s 50% stake in Def Jam Recordings—subsequently bringing the label into their fold. Following PolyGram’s acquisition of the company, Def Jam released Warren G's Regulate...G Funk Era, which went triple platinum and effectively revived the label. The album sold nearly 2.7 million copies within five months of it's release.
Def Jam remained in the black, as its veteran star LL Cool J released his widely successful album Mr. Smith in 1995. The label later signed a then-teenaged Foxy Brown, whose debut album Ill Na Na became a platinum seller in 1997. The same year, Def Jam struck up a distribution deal with Roc-A-Fella Records, and soared to even greater heights with rapper Jay-Z as its central star as the decade drew to a close. PolyGram acquired an additional 10% in Def Jam Recordings in 1995, further strengthening their ownership of the company. Shortly thereafter, “Rush Associated Labels” was renamed “Def Jam Music Group.”
Def Jam joins Universal Music Group
In 1998, PolyGram was purchased by Seagrams and merged into its Universal Music Group. Following Universal Music Group’s takeover of PolyGram, it purchased the remaining interest of Def Jam Recordings from Russell Simmons for a reported $100 million. Simmons went on to focus more on his Phat Farm clothing line and the Hip-Hop Summit Action Network (HSAN).  Universal merged Def Jam with Island Records to form The Island Def Jam Music Group. In spite of the formation of IDJMG, Def Jam and Island continue to operate as separate imprints underneath the bigger umbrella.
Lyor Cohen was appointed president of IDJMG, and Kevin Liles succeeded him as president of Def Jam. In 1999, Def Jam created an R&B spin-off label called Def Soul Records, which inherited many of Island Records’ urban artists, including Dru Hill, Sisqo, The Isley Brothers and Kelly Price. Def Soul also issued recordings by Musiq, Montell Jordan, Case, 112, Patti LaBelle, and Christina Milian.
Also in 1999, Def Jam also began distributing releases by Murder Inc. Records, run by former Def Jam executive Irv Gotti. Murder Inc.'s roster of artists would include Ja Rule, Ashanti, Vita. The following year, it launched another subsidiary, Def Jam South, which focused on Southern rap and distributed releases from labels such as Disturbing tha Peace Records, whose successful artists have included Ludacris, Chingy, and Bobby Valentino. Def Jam South would begin distributing Slip-N-Slide Records releases, featuring Trina, Rick Ross, and others, in 2006.
Def Jam in the 2000s
In 2002, Def Soul was absorbed into its Def Jam parent. A year later, Murder Inc. became the center of a money laundering investigation involving illegal profits from drug trade,  leading to the label's eventual release from its distribution contract by 2005. Roc-A-Fella Records was sold to the company in 2004, by which time it had launched the career of producer turned rapper Kanye West.
The same year, Cohen left IDJMG for Warner Music Group, and was replaced by former Arista executive L.A. Reid. An unhappy Liles eventually decided to follow Cohen to Warner.  A bidding war for Jay-Z's contract began, and Reid appointed Jay-Z president and CEO of Def Jam. 
Under Jay-Z's leadership, Def Jam launched new successful acts such as pop singer Rihanna and R&B singer Ne-Yo. Jay-Z stepped down from his position as Def Jam president at the end of 2007, remaining with Roc-a-Fella/Def Jam as a recording artist.  Following Jay-Z's resignation as president, L.A. Reid took over leadership of the label, as opposed to hiring a replacement.
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