JX (Korean: 제이엑스) is a South Korean duo, composed of Kim Jae-joong, and Kim Jun-su, former members of JYJ and TVXQ. Their group name is taken from the initial letters of each member's present stage names, J-JUN and XIA. The duo is co-managed by their agencies iNKODE and Palmtree Island.

Kim Jae-joong and Xia Jun-su, along with Park Yoo-chun, debuted as part of the five-member boy group TVXQ! under SM Entertainment in 2003. In 2009, the trio filed a lawsuit against SM Entertainment, seeking to terminate their contracts due to alleged unfair contract, and unfair profit distribution.^[1][2] The case was resolved in their favour,^[3][4][5] and they left SM Entertainment to form JYJ in 2010^[6] with CJeS Entertainment.^[7]

JYJ continued to be active until 2015, and after completing their mandatory military service in 2018, Yoo-chun was removed from the group due to multiple incriminating allegations.^{[8][9][10][11]} Subsequently, CJeS Entertainment announced his retirement from the entertainment industry.^[12][13]

In 2021, Xia Jun-su left CJeS Entertainment and established his own agency, Palmtree Island.^[14] Jae-joong also left CJeS Entertainment in 2023 and founded his own agency, iNKODE.^[15]

Since 2018 predating their official formation as JX, Kim Jae-joong and Xia Jun-su have been in a few engagements, without officially addressing themselves as JYJ. Notably in March 2022, they released the song "Sixth Magnitude Star" for a Japanese drama,^[16] and also collaborated again for Dream Concert 2023, introducing themselves and performing together as Jae-joong and Jun-su.^[17]

On September 6, 2024, Kim Jaejoong and XIA Junsu announced their collaborative venture, JX and plans to held their 20th anniversary concert titled IDENTITY in KSPO Dome from November 8–10, 2024.^[18][19]