Kim Hye-yoon is a South Korean actress and model. She first became known through her portrayal as Kang Ye-seo in JTBC's television series Sky Castle (2018–2019) and received her first leading role in television with MBC's Extraordinary You (2019) and her first leading role in film with The Girl on a Bulldozer (2022). She has been dubbed by various Korean media as the Nation's Little Sister.

Sky Castle is a South Korean television series starring Yum Jung-ah, Lee Tae-ran, Yoon Se-ah, Oh Na-ra, and Kim Seo-hyung. It aired on JTBC on Fridays and Saturdays at 22:50 (KST), from November 23, 2018, to February 1, 2019.