Kim Wonjoo (born July 29 1987 in Jeongeup, South Korea) is a South Korean singer best known as a member of the vocal duo 2F. He debuted in 2008 with the EP First Kiss, followed by the 2009 EP Voice Of Autumn and the 2010 releases The 3rd Generation, Baby Baby+4MEN, and U (a collaboration with E‑Tribe). That same year he contributed to the soundtrack for the SBS drama Secret Garden with "Here I am" and appeared on the OST for Bad Guy with "Don't Smile, Don't Cry"; he also participated in the YWHO Winter Serenade project. In December 2011 Kim released the EP Winter Sonata, and in October 2013 he released the single "4MEN The Solo Project #2" under the 4MEN label. Subsequent releases include the 2013 EPs The Artist (June 7), The 5th Album Vol. 1 (실화) (January 28), and The 5th Album Vol. 2 (Thank You) (May 8). Kim’s work has appeared on various Korean drama soundtracks and he has performed on MBC’s Masked Singer in 2018. The track "Always You" on the soundtrack for Recipe for Love was released in April 2026 and entered Melon's Top 500 Melon domestic chart at rank 104 the same week.