Flow-war was a Japanese rock band active from 2002 to 2004. The group originally formed under the name flower in 2002 before changing its name to flow-war in 2003. The band was signed to the ZAIN RECORDS label and consisted of vocalist Nozaki Shimpei (also credited as Oizaki Shimpei), guitarist Sugimoto Issei, bassist Mitsuzono Shoutarou, and drummer Kurose Kaichi. Arranger Oshima Kosuke frequently collaborated with the band on their recordings.

The band is best known for its contributions to the anime series Saiyuki Reload. Flow-war performed the first ending theme song ID for Saiyuki Reload, which was used for episodes one through thirteen. The single for ID was released on November 12, 2003, and also included the B-side tracks Yako Chuu and Everyday, along with an instrumental version of the title song. Following this, the band performed the ending theme song Mitsumete Itai for the sequel series Saiyuki Reload Gunlock. This single was released on April 28, 2004, and featured the tracks Gold Finger and Mikaduki ga Waratteiru.

The band released a self-titled mini-album called flower under their original name in 2002. After the name change, they released a full-length album titled ID on June 23, 2004, which compiled their major singles along with new tracks such as Keikyoku no Michi, Ai no Kara, and Buki wo Tore. Both of their anime theme songs appear on this album in their full versions. The songs were also featured on various soundtrack collections for the Saiyuki Reload anime series. Flow-war disbanded in the autumn of 2004, bringing a close to their brief career.