Kim You-jung (Korean: 김유정; born September 22, 1999) is a South Korean actress. She started out as a model for a confectionery brand at the age of four and after her acting debut in 2003, Kim became one of the most in-demand child actresses in South Korea leading her to be called "Nation's Little Sister". Kim had her first starring role in the historical romance Love in the Moonlight in 2016 which catapulted her to fame as a leading actress in television and film. She ranked 8th on the Forbes Korea Power Celebrity list in 2017, the youngest to be included in the Top 10 at the age of 17.
Through her roles in several acclaimed historical television series in her teens, Kim has been referred to as "Sageuk Fairy" by media outlets. Since then, she further received attention for her performances in the romantic-comedy Backstreet Rookie (2020), historical fantasy Lovers of the Red Sky (2021), teen romance film 20th Century Girl (2022), fantasy romance My Demon (2023–2024), and psychological thriller Dear X (2025). She gained the nicknames "Nation's First Love" following her performance in 20th Century Girl.
Kim was born in Seongdong District, Seoul, South Korea on September 22, 1999 as the youngest of three siblings. Her older sister, Kim Yeon-jung, debuted as an actress in 2017. She attended Goyang High School of Arts and graduated in January 2018. Kim deferred taking the national College Scholastic Ability Test in 2017, and instead decided to focus on her acting career.
2003–2011: Beginnings as a child model and actress
Kim debuted as a model for a confectionery brand at the age of four. After her acting debut when she was four, she quickly became one of the most in-demand child actresses in Korea. By the time she was a fifth grader, Kim had already appeared in 13 television dramas and 15 films.
In 2008, she received her first acting award as Best Child Actress for action-adventure series Iljimae and historical drama Painter of the Wind. This was followed by acclaimed performances in Dong Yi (2010) and Flames of Desire (2010). Grudge: The Revolt of Gumiho (2010) marked Kim's first major role that wasn't the childhood counterpart of the female protagonist.
2012–2015: Rising popularity and teen roles
She rose to popularity in 2012 when she starred in the fantasy-period drama Moon Embracing the Sun, which reunited Kim with Grudge: The Revolt of Gumiho costar Lee Tae-ri and Iljimae costar Yeo Jin-goo. Moon surpassed 40% ratings and gained "national drama" status. For her good portrayal of the young protagonist, she was nominated for Best New Actress in the 48th Baeksang Arts Awards, and she won Best Young Actress Award in the 1st K-Drama Star Awards and 2012 MBC Drama Awards. She followed this with a well-received turn in May Queen (2012) and a supporting role in the 2013 film Commitment, and family drama Golden Rainbow (2013).
In 2014, Kim's performance as a teenage bully in Thread of Lies drew critical acclaim and she was nominated for the Best New Actress in Blue Dragon Film Awards. She next played a traditional funeral singer (or "gok-bi") in the single-episode Drama Special anthology, and was cast in the horror mystery Room 731, an English-language graduate thesis film by USC filmmaker Kim Young-min. This was followed by a starring role in the period drama Secret Door. Kim also began hosting music show Inkigayo in November 2014 and left the show in April 2016.
In 2015, she starred in the television series Angry Mom which tackled bullying and school violence. The same year, she reprised her role as a cat-turned-woman in Love Cells, a two-season web series adapted from the webtoon of the same title and played a murderer's daughter in the thriller film Circle of Atonement.
In August 2016, Kim starred in her first adult leading role in the youth historical drama Love in the Moonlight as Hong Ra-on - a girl who was raised as a boy and eventually became a eunuch of Crown Prince of Joseon, played by Park Bo-gum. A domestic hit, Moonlight achieved peak audience rating of 23.3% and its popularity was referred to as "Moonlight Syndrome". Kim won an Excellence Award for portraying Moonlight's cross-dressing heroine at the 30th KBS Drama Awards. It also earned her a Baeksang Arts Award for Most Popular Actress – Television.
In 2017, she starred with Cha Tae-hyun in the romantic-comedy film Because I Love You. In 2018, Kim starred in the romantic-comedy drama Clean with Passion for Now, based on the webtoon of the same name. She played an employee at a cleaning company who doesn't care about dirtiness. In 2020, Kim was cast in the romantic-comedy drama, Backstreet Rookie, alongside Ji Chang-wook, based on a webtoon of the same name and played the role of a former high school troublemaker who becomes a part-time employee at a convenience store. The actress is said to be attending action school in order to perform her own stunts and the production staff stated, "Kim has been working hard on fight scenes and wire action for her role as Jung Saet-byul. Please anticipate the unique transformation that Kim will undergo". During the 2020 SBS Drama Awards held on December 31, 2020, Kim was chosen to be the main host together with Shin Dong-yup. At the same event, Kim was awarded Excellence Award, Actress in a Miniseries Fantasy/Romance Drama for her great portrayal of her role as Jung Saet-byul in the series Backstreet Rookie.
In December 2020, Kim was confirmed as the female lead role in the historical-fantasy drama Lovers of the Red Sky adapted from the novel written by Jung Eun-gwol. The drama premiered in August 2021 on SBS TV and Kim played the titular role of Hong Chun-gi, the Joseon dynasty's only female painter, alongside Ahn Hyo-seop as Ha Ram, a blind astrologer. The series reunited Kim with director Jang Tae-yoo after 13 years since Painter of the Wind (2008) where Kim played the childhood counterpart of the protagonist. In 2021, Kim appeared in the mystery thriller Netflix film The 8th Night in the role of an enigmatic psychic. In December 2021, she made a cameo appearance in the final episode of Coupang Play's television series One Ordinary Day. At the end of 2021, Kim hosted 2021 SBS Drama Awards with Shin Dong-yup for the second year in a row, receiving Top Excellence Award, Actress in a Miniseries Genre/Fantasy Drama and winning Best Couple Award with Ahn Hyo-seop for the drama Lovers of the Red Sky at the same event.
2022–present: Theater debut and continued success
In 2022, Kim reunited with the director and cast members of Love in the Moonlight in the TVING travel entertainment program Young Actors' Retreat. The same year, she appeared in the Netflix film 20th Century Girl playing the title role as 17-year-old Na Bo-ra in 1999. Kim made her theatrical stage debut in January 2023, taking part in Kim Dong-yeon's play Shakespeare in Love, adapted from the 1998 film of the same name. She played the role of Viola de Lesseps, the daughter of a wealthy merchant, who disguises herself as a man named Thomas Kent to become a theater actress, which was taboo for women at the time. The play received favorable reviews and Kim's performance was praised by the critics and the audience. In March, she made a special appearance in Jason Kim's film My Heart Puppy as Ah-min, a disabled girl who looks after abandoned dogs.
In January 2023, she starred in SBS television series My Demon where she portrayed Do Do-hee, a chaebol heiress. The series was released in November 2023. In 2024, Kim made a special appearance in the Netflix original series Chicken Nugget. She portrayed the character Choi Min-ah, the daughter of a company president, she becomes embroiled in a comedic mishap when she mistakenly believes a new machine is designed to alleviate her fatigue and accidentally turns into a chicken nugget.
In September 2025, Kim was honored as the inaugural recipient of the Busan International Actors Award at the 30th Busan International Film Festival, recognizing her contributions to the Korean film industry. Later that year, she starred in the TVING original series Dear X, which premiered on November 6, 2025. She played the role of Baek A-jin, a sociopath who hides her cruel nature behind a beautiful appearance, marking a significant transformation in her acting career. Kim's performance received widespread praise with The Korea Times calling it "chilling" which "anchors [the] story about trauma [and] manipulation". The series achieved global success, topping OTT charts in 108 countries shortly after its release.