Kim Jun-su (; born 15 December 1986) or simply Junsu, also known by the stage name Xia (stylized as XIA; ; ) is a South Korean singer-songwriter, dancer, and stage actor. He is a member of the Korean pop group JYJ, and was one of the original members of boy band TVXQ. He has been dubbed as the best idol vocalist in the Korean pop industry since 2011. For having intense vocal talent, he is also regarded as the best Musical actor from the sector of K-Pop idols.
Kim made his debut in 2003 as a member of TVXQ, a boy band produced and formed by South Korean record label and talent agency S.M. Entertainment, having previously been a trainee for six years. He had released four Korean albums, four Japanese albums, thirty Japanese singles and several Korean singles during his first six years in the music industry as TVXQ. In 2009, Kim and fellow TVXQ members Kim Jaejoong and Park Yoochun filed a lawsuit against SM Entertainment, arguing that their exclusive contracts were unilaterally disadvantageous towards the artists and should be invalidated. The Seoul Central District Court ruled in favor of the three and granted an injunction suspending their contracts. The trio reunited and subsequently formed JYJ (formerly known as JUNSU/JAEJOONG/YOOCHUN in Japan). As JYJ, Kim has released one English album, two Korean albums, two Japanese EP, and one Korean EP.
Kim began his solo career in 2010 with the release of Japanese single Xiah, which peaked at number-two on Japan's Oricon singles chart. The same year, he took the role of Wolfgang in his debut musical Mozart!, receiving critical acclaim and commercial success. After the release of Xiah, Kim's solo music career was sent into hiatus because of a discord between him and his Japanese label Avex Trax that led to the sudden suspension of all his activities in Japan. In May 2012, he released his first full-length Korean solo studio album Tarantallegra, while being represented by new management agency C-JeS Entertainment. Following the release, he embarked on his first headlining world tour. He returned with his second Korean solo studio album, Incredible, in July 2013.
Despite limitations in media coverage and promotional activities caused by a ban in the Entertainment Departments of South Korea's three main terrestrial broadcasters resulting from SM Entertainment's interference, Kim's first and second studio album reached top two on the Gaon albums chart in South Korea, as well as reaching number-ten and number-five on the Billboard World Albums chart for Tarantallegra and Incredible, respectively. He is also known for being able to sell out tickets for his concerts and musicals within minutes, dubbed "the ticket power" by South Korean media.