Kim Hyo-yun (Hangul: 김효연, Romanized: Kim Hyo-yun, born September 22, 1989), known professionally as Hyo-Yeon or simply HYO, is a South Korean female singer and member of the girl group Girls' Generation and its subunit Girls' Generation-Oh! GG. She serves as a backup vocalist, main dancer, and main rapper in the group.
