Kim Hye-yoon (born November 10, 1996) 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 with MBC's Extraordinary You (2019). She has been dubbed by various Korean media as the Nation's Little Sister.
 Kim Hye-yoon was born on November 10, 1996, on Seongnam, Gyeonggi Province, South Korea. She has always dreamed of becoming an actress since her third year of middle school and has dedicated herself by attending an acting academy, auditioning, and taking on small roles earnestly to prepare and learn about the field.
 She completed her studies at Konkuk University, majoring in film studies in 2019, after receiving a full scholarship, which supported her throughout her college years. Several of her works were featured at various student film festivals.
 Kim Hye-yoon debuted as an actress in the 2013 KBS2 TV Novel's Samsaengi, as the teenage era of a supporting character. After landing a memorable role in the 2014 OCN's crime thriller Bad Guys, Kim focused on her studies and only made guest appearances in several dramas, as she had received a full scholarship in 2015 to Konkuk University, one of Korea's leading universities.  Her biggest role during that period was a supporting character in the 2017 action thriller film Memoir of a Murderer.
 Leading up to her college graduation in February 2019, Kim began auditioning for bigger roles, including for JTBC's satire drama Sky Castle. The massive success of the series, along with her distinctive role as an ambitious and unfriendly but ladylike high school girl, launched her to stardom and won her the 55th Baeksang Arts Awards for Best New Actress.
 In 2019, Kim starred as the protagonist for the first time with MBC's school fantasy drama Extraordinary You, based on the hit Daum webtoon July Found by Chance. She received further recognition, winning both New and Excellence Actress at the MBC Drama Awards. During the same year, she joined as one of the lead cast in the psychological thriller film Midnight, where she portrayed the role of So-jung.
 Kim received her first main leading role in film with 2020 production The Girl on a Bulldozer. In the same year, she also confirmed to star in the 2021 pre-produced JTBC series Snowdrop, in which she reunited with the production team of hit drama Sky Castle.
 Near the completion of Snowdrop filming process, Kim received the offer to star in tvN's 2021 historical procedural Secret Royal Inspector & Joy. The drama premiered ahead of Snowdrop.
 In 2022, The Girl on a Bulldozer was released theatrically, and Kim's performance as Goo Hye-young has received critical acclaim and garnered her several awards from prestigious shows such as the Blue Dragon Film Awards and Grand Bell Awards for Best New Actress, as well as the Rising Star Asia Award at the New York Asian Film Festival. Notably, Kim was also nominated for the Best New Actress Film category at the 59th Baeksang Arts Awards. With the film's success, Kim earned a total of 10 nominations, winning 6 of them. Her achievements were further recognized by Forbes, which featured her in their Forbes 30 Under 30 list.
 After focusing her attention on the promotion and production of her two films, The Girl on a Bulldozer and Ditto throughout 2022, Kim is set to return to the small screen with tvN's time slip fantasy drama Loverly Runner. The drama is scheduled to premiere in 2024.