Seo Hyun-jin (born February 27, 1985) is a South Korean actress and singer. Seo debuted as the vocalist of South Korean girl group M.I.L.K. in 2001 and continued until the group disbanded in 2003. She contributed songs as a solo artist after the group broke up before she transitioned into acting in 2006.

Seo made her acting debut in the musical The Sound of Music (2006) then followed by appearances in several television series and film. She is best known for her leading role as Oh Hae-young in the romantic comedy TV series Another Miss Oh (2016), which gained her wider recognition. Seo has since gone on to have key parts in the medical melodrama Dr. Romantic (2016–2017), romance dramas Temperature of Love (2017), The Beauty Inside (2018), and You Are My Spring (2021), and the legal drama Why Her (2022).