| Toshiko Koshijima | |
| Birth Name: | Toshiko Koshijima (越島稔子) |
| Alias: | Koshiko [fan nickname] (こしこ) [written in Hiragana] |
| Birth Date: | 3 March 1980 |
| Birth Place: | Kanazawa, Ishikawa, Japan |
| Genre: | Pop, electronic, Shibuya-kei |
| Occupation: | Singer |
| Years Active: | 1997-present |
| Label: | Contemode, Warner |
| Associated Acts: | Capsule |
is a Japanese singer. Along with composer, record producer and DJ Yasutaka Nakata, she is the lead vocalist of the electronica band Capsule, which she formed in 1997 with Nakata when they were both 17. Their formal debut came in 2001 with the release of the single "Sakura". Two more singles and their debut album, High Collar Girl, followed the same year.
Koshijima has worked exclusively as part of Capsule since the group's inception, acting as lead vocalist for all of the band's fifteen albums to date.