Folie à Deux (English: "A Madness Shared by Two") is the fourth studio album by American rock band Fall Out Boy. Produced by Neal Avron, the album was recorded from July to September 2008 at The Pass Studios and The Casita in Hollywood, California. As the follow-up to the band's commercially successful 2007 effort Infinity on High, it was released by Island Records on December 10, 2008, after the original November 4 release was postponed to avoid conflicts with the United States presidential election. Like the band's two previous releases, Folie à Deux was composed by lead vocalist and guitarist Patrick Stump. The lyrics were penned by bassist Pete Wentz. With regard to the writing process, the band considered Folie à Deux to be their most collaborative record yet.
The album was recorded in relative secrecy compared to the press of that of its predecessor. The recording sessions inspired lyricism that relate to decaying relationships, moral dilemmas, and societal shortcomings with a political edge. It is the first Fall Out Boy album with lyrics that are rarely autobiographical; this shift led to a musical style change that resulted in a further musical departure from the band's previous albums. Fall Out Boy recruited several guest artists for Folie à Deux, as well as employing instruments and recording techniques previously unfamiliar to the group. To promote the album, the band launched a viral campaign based around a Big Brother-type organization named "Citizens For Our Betterment" (CFOB) and embarked on an extensive tour schedule.
Folie à Deux was released in the United States on December 16, 2008, and received favorable reviews from most music critics, although fan opinions were mixed. Positive reviews focused on the creativity and various styles touched on, while the more negative reviews expressed concern that the record was overly indulgent. The album debuted at number eight on the US Billboard 200 chart but was less commercially successful than Infinity on High. It was certified gold by the Recording Industry Association of America (RIAA) after 500,000 copies were shipped. The album spawned three singles. "I Don't Care," the first single, reached number 21 on the Billboard Hot 100 and was certified platinum. Folie à Deux was Fall Out Boy's last studio album released before the band's late 2009 hiatus.