Mucc (Japanese: ムック, Hepburn: Mukku; stylized as MUCC) is a Japanese visual kei rock band, formed in Ibaraki Prefecture in 1997. The classic line up of Tatsuro on vocals, Miya on guitar, Yukke on bass, and Satochi on drums was solidified in 1999 following the departure of original bassist Hiro. After 24 years, Satochi retired from the music industry in October 2021, leaving Mucc a trio. They have released 17 studio albums, with 2020's Aku being their highest-charting. Although predominately a heavy band both lyrically and musically, Mucc is known for switching between music genres and styles frequently. Kerrang! included their fourth studio album Kuchiki no Tō (2004) on a list of 13 essential Japanese rock and metal albums.

Mucc was formed in 1997 by guitarist Miya, vocalist Tatsuro (then called "Tattoo"), bassist Hiro, and drummer Satochi. High school students who had been friends since primary school. They had their first concert at the Shimamura Music store in Mito, Ibaraki on May 4. Satochi was only a support musician, but decided to officially join after the concert because of how much fun he had. The name Mucc is often believed to have been taken from a character in the children's TV show Hirake! Ponkikki. However, Miya stated he chose the name because it is easy to remember and is not something you associate with music. When he later learned that the English word "muck" means "filth", he thought that was also good. The band is also known by the nickname "69" since the numbers six and nine can be pronounced "mu" and "ku", respectively, in Japanese. They have played with this number throughout their career, such as dubbing June 9 "Mucc Day", and providing live broadcasts that last 690 minutes. Fans of the band are known as "Muccer" (夢烏（ムッカー）, Mukkā).

Originally playing covers of bands such as The Blue Hearts and Glay, Malice Mizer and The Mad Capsule Markets Mucc handed out their first demo tape, No!?, in December 1997. After graduating high school, the band moved to Tokyo. On March 3, 1998, they handed out copies of their second demo tape, Aika, and on December 1, they gave out a limited 100 copies of their third, Tsubasa wo Kudasai. In 1999, Hiro left the band on February 14 and was replaced on bass by Miya's childhood friend Yukke on February 22. In July, Mucc had their first tour, where they handed out demo tapes of Aka at every venue. On December 25, they had their first official release, the EP Antique. On June 8, 2000, Tattoo changed his stage name to his current name of Tatsuro. They released their first album, Tsūzetsu, on January 7, 2001. It was followed by the EP Aishū on December 25. In 2002, the band signed to Danger Crue, establishing their own sublabel Shu (朱), and released their second album, Hōmura Uta. That year they held a concert titled En (えん), which featured acts from different genres. They have continued to hold En events sporadically since.

Mucc signed to Universal in 2003, and released their major label debut single "Waga, Arubeki Basho" on May 3. Third studio album Zekū followed on September 3. Their first live DVD, Nihon Rettou Konton Heisei Kokoro no Naka, was released on December 10. The band held a guerrilla live at Shinjuku Station on June 9, 2004, in front of an estimated 5,000 people. Their fourth studio album Kuchiki no Tō was released on September 1 and supported by the Sōran Shūkyō fall tour, which ended on October 31 at Hibiya Open Air Concert Hall. In January 2005, Mucc held a joint tour with Balzac. Kuchiki no Tō Live at Roppongi, their first live album, was released on January 26.

Mucc debuted in Europe in August 2005, including a performance at Wacken Open Air. They released the album Hōyoku on November 23. Mucc released two albums in 2006, 6 and Gokusai, and performed in the United States at the Otakon anime convention. They ended a world tour on June 6 with their first concert at the Nippon Budokan. 2007 marked Mucc's 10th anniversary. They released two compilation albums, Best of Mucc and Worst of Mucc; the latter includes rare songs from their indie years. In addition to opening for Guns N' Roses on the Japanese leg of their 2007 World Tour, Mucc gave performances in Shanghai, in Finland at Provinssirock, and in the US at JRock Revolution Festival. They also performed at the Abstinence's Door #001 event hosted by D'erlanger, and their song "Chain Ring" was used as the ending theme to the Zombie-Loan anime adaptation. They held a special 10th anniversary concert at the Ibaraki Prefectural Cultural Center in November.

Throughout 2008, Mucc participated in the Taste of Chaos 2008 tour, which initially stopped at forty cities across the United States and Canada from February to May, along with fellow Japanese bands D'espairsRay and the Underneath. In March, they released the album Shion. After returning to Japan, Mucc performed at the hide memorial summit at Ajinomoto Stadium alongside groups such as X Japan and Luna Sea, and began their own nationwide Rainy Rave tour before performing at the Sweden Rock Festival in June. The Taste of Chaos tour went to Europe in October, and then to Japan in November, where Mucc was the headliner. Mucc then performed at The Fillmore New York at Irving Plaza on December 7, 2008 and the House of Blues in Los Angeles on December 10.

Following the March 2009 release of their ninth studio album Kyūtai, Mucc held a sold-out 16-date nationwide tour from May to June. After performing in Sweden at Metaltown Festival in June, their Solid Sphere Tour began with a live in Russia on October 3, before featuring their first shows in Latin America (Chile and Mexico). The band completed the tour on November 16 in Japan at the JCB Hall. Mucc started 2010 with a concert on February 14 at the NHK Hall, before traveling to Taiwan for the March 14 Megaport Music Festival. The single "Yakusoku" was used as the opening theme to Night Raid 1931. The band performed at Summer Sonic on August 8. Returning to being an indie band on Danger Crue Records, Mucc released Karma on October 6. Three days later, they performed at a cultural festival at Yukke's alma mater Ibaraki Prefectural Ogawa High School, which was closing. The Chemical Parade tour took place between October and December.

A European leg of the Chemical Parade tour was held in five countries throughout January 2011, while two Asian shows took place in April. At their May 21 and 22 Nippon Budokan shows, the band announced they would be signing to major label Sony Music Associated Records. The single "Akatsuki" was first sold exclusively at those concerts, before later being available as a digital download with all proceeds donated to aid the victims of the 2011 Tōhoku earthquake and tsunami. On July 15, Mucc performed at a concert commemorating the first anniversary of the death of Daisuke, former singer of the band Kagerou. They also performed at the V-Rock Festival '11 held at Saitama Super Arena on October 23, before releasing the single "Arcadia" which featured DJ Daishi Dance in November.