Toshio Hosokawa (細川 俊夫 Hosokawa Toshio?, born 23 October 1955 in Hiroshima, Japan) is a Japanese composer of contemporary classical music.
Hosokawa studied with Yun Isang at the Berlin University of the Arts. Since 1998, Hosokawa has served as Composer-in-Residence at the Tokyo Symphony Orchestra. In 2004, Hosokawa became a guest professor at Tokyo College of Music. In 2001, Hosokawa became a member of Akademie der Künste, Berlin.

Invited by Walter Fink, he was the 18th composer featured in the annual Komponistenporträt of the Rheingau Musik Festival in 2008, in chamber music, played by the Arditti Quartet and Mayumi Miyata (Shō), and the oratorio Voiceless Voice in Hiroshima, performed by the WDR Symphony Orchestra and Choir, Cologne conducted by Rupert Huber.