DEEN is a Japanese pop and rock band that has been active since its formation in 1992. The band is best known for its work in the 1990s and 2000s, particularly for contributing several theme songs to popular anime series and video games. As a musical group, DEEN is primarily a band entity rather than a solo artist, with its core members responsible for vocals, songwriting, and instrumentation.

The band made its major debut on March 10, 1993, with the single Konomama Kimi Dake wo Ubaisaritai, which became a million-selling hit and established the group as a significant act in the Japanese music industry. Their early work was associated with the Being agency and B-Gram Records. Over the course of their career, DEEN has achieved the notable distinction of having both their debut single and debut album certified million-sellers by the Recording Industry Association of Japan.

DEEN has a deep catalog of songs tied to anime, television, and video game properties. One of their most recognized anime contributions is the song Hitori Ja Nai, which was used as the first ending theme for the anime series Dragon Ball GT. Another significant track is Kimi ga Inai Natsu, which served as the fourth ending theme for the long-running detective series Detective Conan, also known as Case Closed. The band also contributed the song Kimi Sae Ireba as the third opening theme for the anime Chuuka Ichiban, known in English as Cooking Master Boy.

Beyond anime television series, DEEN has a strong connection to video game soundtracks. The band is particularly associated with the Tales series of role-playing games. Their song Yume de Aru Youni was adopted as the theme for the 1997 game Tales of Destiny. Over a decade later, the single Eien no Ashita was used as the theme song for Tales of Hearts, released in 2008. This single debuted at number six on the Oricon weekly charts, marking the band's highest position on the chart in twelve years.

The musical identity of DEEN has evolved since its formation. The band originally had a sound rooted in pop rock and J-POP. Over time, they have incorporated classical music elements into their arrangements and have also referred to their style as Neo-AOR. The band has also experimented with cover songs, including a version of Kyu Sakamoto's classic Miagete Goran Yoru no Hoshi o.

The lineup of DEEN has changed several times since its inception. The constant core members throughout the band's history have been vocalist and lyricist Shuichi Ikemori, and keyboardist Koji Yamane, who also serves as the band's leader. Other long-standing members included guitarist Shinji Tagawa and drummer Naoki Uzumoto, both of whom have since left the group. Drummer Uzumoto departed in 2000, while guitarist Tagawa left in 2018. As of 2023, the band continues as a duo consisting of Ikemori and Yamane.

In terms of industry significance, DEEN achieved substantial commercial success in the 1990s, selling over 15 million compact discs. They are recognized as one of the acts that defined the Being era of Japanese pop music. Their achievement of having both a debut single and debut album surpass one million sales in Japan is a rare feat that places them in an exclusive category of artists. The band has continued to release new music and perform live, maintaining a dedicated fanbase and a legacy as a lasting presence in the Japanese music industry.