Relapse is the sixth studio album by the American rapper Eminem. It was released on May 15, 2009, through Shady Records, Goliath Artists, Aftermath Entertainment, WEB Entertainment, and Interscope Records. It was Eminem's first studio album after a hiatus following Encore (2004), due to writer's block and an addiction to prescription sleeping medication. Eminem's mentor Dr. Dre produced every track except for "Beautiful", which Eminem produced himself. Guest appearances include Dr. Dre and 50 Cent; a reissue, released on December 21, adds Drake, Kanye West, Lil Wayne, and Dr. Dre.

Relapse is a horrorcore album about drug rehabilitation and relapse. It features the return of Eminem's Slim Shady alter ego, and Eminem described it as reminiscent of The Slim Shady LP (1999) and The Marshall Mathers LP (2000). The concept album features Eminem as a serial killer using various accents, and includes skits with performances from Dominic West, Paul Rosenberg, and Angela Yee, among others.

Relapse was promoted with five singles: "Crack a Bottle" (which topped the US Billboard Hot 100), "We Made You", "3 a.m.", "Old Time's Sake", and "Beautiful". It received mixed reviews; critics generally praised its production, but were divided over the writing and criticized Eminem's accents. Nonetheless, Relapse won Best Rap Album at the 52nd Annual Grammy Awards, while "Crack a Bottle" won for Best Rap Performance by a Duo or Group. While Eminem expressed dissatisfaction with Relapse following its release, it developed a cult following and underwent a critical reevaluation; it is now regarded as one of Eminem's best albums, with praise for its humor, performances, and creativity.

One of the most anticipated albums of 2009, Relapse debuted atop the US Billboard 200, with 608,000 copies sold in its first week, staying at top for two weeks. It also reached number one in 12 other countries. In 2022, it was certified triple platinum by the Recording Industry Association of America (RIAA). A sequel called Relapse 2 was planned, but canceled in favor of Recovery (2010).

After releasing Encore in 2004, Eminem planned to take some time off from recording his own music to become a hip-hop producer for other rap acts, especially for the artists signed on his own label, Shady Records. However, Eminem entered his hiatus earlier than expected after cancelling the European leg of the Anger Management Tour in the summer of 2005 because of exhaustion and an addiction to prescription sleeping drugs. Eminem faced a number of setbacks in 2006, with his remarriage to former wife Kimberly Scott lasting only eleven weeks before a second divorce, while his best friend and fellow rapper Proof was later shot and killed during an altercation outside a Detroit nightclub. Devastated, Eminem relapsed into prescription drug abuse and became increasingly reclusive. In a June 2009 interview for XXL, Eminem elaborated on the impact of Proof's death on him, stating:

"Everyone felt Proof's loss, from his kids, to his wife, to everyone. But, for some reason, in hindsight, the way I felt was almost like it happened to just me... Maybe at the time I was a little bit selfish with it. I think it kind of hit me so hard. It just blindsided me. I just went into such a dark place that, with everything, the drugs, my thoughts, everything. And the more drugs I consumed, and it was all depressants I was taking, the more depressed I became, the more self-loathing I became..."

Speculation on an upcoming album by Eminem which was named King Mathers confirmed by Cashis and many different leaks, was reported since early 2007 from announcements made by artists 50 Cent and Stat Quo, former members of Shady Records. Also, rapper Bizarre – a member of the hip-hop group D12 – stated that the release of the group's third studio album was on hold because Interscope Records wanted to release Eminem's album first. By the end of the year, additional musicians associated with Shady Records – including The Alchemist, Bishop Lamont, Cashis and Obie Trice – had confirmed on different occasions that the rapper was effectively working on a new album. On September 12, 2007, during a call at the radio station WQHT Hot 97, Eminem stated that he was in limbo and was not sure whether he would release any new material in the near future. He then elaborated that at that point he was constantly working in the recording studio and had come to terms with his personal issues. However, in December 2007, he was hospitalized because of an overdose of methadone that nearly killed him. In early 2008, he began a 12-step program to recover from his addiction; in a later interview, he said that he got sober on April 20, 2008. He has stayed sober since then.

Eminem continued recording throughout 2005 and released most of this work on his Shady Records compilation album Eminem Presents: The Re-Up. He also wrote a track called "Beautiful" when he was in rehab and finished it after he got out of rehab in 2005. It became the fifth and final single on Relapse, and also one of the only songs on the entire album that Eminem recorded when he wasn't sober. Eminem began the recording stages of Relapse in mid-2008, after completing a 12-step program to control his drug addiction. Record producer and long-time Detroit collaborator Jeff Bass of the Bass Brothers worked with Eminem on 25 tracks, two years after the rapper had received treatment for his sleeping pill addiction in 2005. Depressed by Proof's death, Eminem fell into a period of "writer's block", where he felt everything he wrote was not worth recording. To compensate for this, Bass chose to follow a production style that would allow the artist to rap "off the top of his head, as opposed to writing a story". Eminem would then freestyle or record vocals one line at a time before interrupting and then recording another line. At the same time, according to Eminem's song rights supervisor Joel Martin, the rapper began to collect additional songs without noticing it. He would often record or produce material initially intended for the musical projects of other artists, but end up with tracks he really liked.