|Stage Name||Birth Name||Position||Birthday||Age||Height||Star Sign Sort descending||C Y||BT|
|Donghan 동한||Kim Donghan||Maknae||19||181 cm or 5'11½"||Cancer||Tiger||O|
|Kenta 켄타||Takada Kenta||Vocal||23||173 cm or 5'8"||Capricorn||Dog||B|
|Sanggyun 상균||Kim Sanggyun||Rapper||22||178 cm or 5'10"||Gemini||Pig||O|
|Taehyun 태현||Noh Taehyun||Leader, Dancer||24||168 cm or 5'6"||Libra||Rooster||A|
|Hyunbin 현빈||Kwon Hyunbin||Rapper||20||187 cm or 6'1½"||Pisces||Ox||B|
|Longguo 용국||Jin Longguo||Vocal||21||175 cm or 5'9"||Pisces||Rat||A|
JBJ 제이비제이 is a project male idol group consisting of six members who previously participated in Mnet's 2017 survival show "Produce 101." The group is managed by Fave Entertainment, while CJ E&M oversees the group's release production. The group officially debuted on October 18, 2017.
The second season of "Produce 101" premiered on Mnet in April 2017. 101 male trainees from various South Korean entertainment companies competed to debut in an 11-member boy group that would promote for two years under YMC Entertainment. The show ended on June 16 with the formation of the project group Wanna One. On the same day, the show's fans named Takada Kenta of Star Road Entertainment, Jin Longguo of Choon Entertainment, Kim Sanggyun of Hunus Entertainment, and Kim Taedong of The Vibe Label (later known as Major Nine), as eliminated trainees they wanted to see debut together as a project group equivalent to the original "Produce 101" I.B.I. The fans tentatively named the group "JBJ," short for "Just Be Joyful." Later on, Roh Taehyun of Ardor and Able (later known as Star Crew Entertainment), Kim Donghan of OUI Entertainment, and Kwon Hyunbin of YGKPlus were added into the fan-imagined group after an Instagram photo that Taehyun posted received positive feedback from fans.
Discussions to officially form and debut JBJ began around early July 2017 between the seven tentative members and their respective agencies. CJ E&M and LOEN Entertainment also participated in the discussions as the intended management companies of the group's releases and activities, respectively. Fave Entertainment, LOEN Entertainment's in-house label, was tasked to be the group's official agency. On July 25, the trainees and companies reached an agreement. The group's contract would last seven months, but LOEN Entertainment expressed that they were open for any discussions to extend the contract. JBJ was tentatively scheduled for debut on September 10 with all seven members, but was later confirmed for debut on October 18 without Kim Taedong.
Kim Taedong's participation in the group was not confirmed because of an ongoing conflict with his agency, The Vibe Label. On July 27, Taedong sent his agency certification of contents and requested for his contract be terminated. Since then, the involved parties, including CJ E&M and LOEN Entertainment, have had numerous meetings to resolve the conflict but, as of September 7, had yet to reach an agreement.
JBJ's first reality show began airing on September 27, 2017, on Mnet M2.