Riyu Kosaka (小坂りゆ [Kosaka Riyu], born January 17 in Yokohama, Kanagawa Prefecture, Japan) is a Japanese pop singer. She is known as the lead vocalist of Konami's J‑pop group, BeForU, and is produced by NAOKI Maeda. In addition to songs for the Bemani series of games, Riyu Kosaka has performed songs for anime, including the ending for Claymore and the opening to Konami's own Sky Girls.

She started her solo career almost as the same time BeForU debuted, and became the first member of the group that achieved a CD release (even before her own group) in 2001, with her first single «true...». In 2004 her first album «begin» was released. She debuted as a major artist in 2006 with the release of her single «Yamato Nadeshiko».