Seo Ju-hyun (born June 28, 1991), known professionally as Seohyun, is a South Korean singer and actress. She debuted as a member of girl group Girls' Generation (and later its subgroup Girls' Generation-TTS) in August 2007, which went on to become one of the best-selling artists in South Korea and one of South Korea's most popular girl groups worldwide. Apart from her group's activities, she has established herself as an actress, notably through her participation in the original and Korean versions of stage musicals including Moon Embracing the Sun, Gone with the Wind and Mamma Mia. She also played a supporting role in the television drama Moon Lovers: Scarlet Heart Ryeo (2016). Seohyun played her first lead role in the television drama Bad Thief, Good Thief (2017).
In 2017, Seohyun released her first extended play Don't Say No, making her the third Girls' Generation member to debut as a solo artist. Later the same year, although Seohyun remains as a member of Girls' Generation, she left SM Entertainment and joined Namoo Actors in 2019 to focus on her acting career.