|Stage Name||Birth Name||Position||Birthday||Age||Height||Star Sign Sort descending||C Y||BT|
|Xuan Yi 선의||Wu Xuan Yi||Dancer||23||166 cm or 5'5½"||Aquarius||Dog||O|
|Dawon 다원||Nam Dawon||Vocal||21||167 cm or 5'5½"||Aries||Ox||A|
|Cheng Xiao 성소||Cheng Xiao Xiao||Dancer||19||167 cm or 5'5½"||Cancer||Tiger||B|
|SeolA 설아||Kim Hyunjung||Vocal||23||165 cm or 5'5"||Capricorn||Dog||A|
|Yeoreum 여름||Lee Jinsook||Rapper||19||161 cm or 5'3½"||Capricorn||Tiger||A|
|Eunseo 은서||Son Juyeon||Vocal||19||168 cm or 5'6"||Gemini||Tiger||B|
|Bona 보나||Kim Jiyeon||Visual||22||163 cm or 5'4"||Leo||Pig||A|
|Yeonjung 연정||Yoo Yeonjung||Vocal, Maknae||18||167 cm or 5'5½"||Leo||Hare||A|
|Mei Qi 미기||Meng Mei Qi||Dancer||19||164 cm or 5'4½"||Libra||Tiger||B|
|Luda 루다||Lee Luda||Sub-vocal||21||157 cm or 5'2"||Pisces||Ox||A|
|Exy 엑시||Chu Sojung||Leader, Rapper||22||166 cm or 5'5½"||Scorpio||Pig||A|
|Dayoung 다영||Lim Dayoung||Vocal||18||161 cm or 5'3½"||Taurus||Hare||A|
|Soobin 수빈||Park Soobin||Vocal||21||159 cm or 5'2½"||Virgo||Rat||AB|
Cosmic Girls 우주소녀, also known as WJSN, is a South Korean-Chinese girl group formed by Starship Entertainment and Yuehua Entertainment. The group is comprised of thirteen members: SeolA, Xuan Yi, Bona, Exy, Soobin, Luda, Dawon, Eunseo, Cheng Xiao, Mei Qi, Yeoreum, Dayoung, and Yeonjung. The members are separated into four subgroups for each letter in "WJSN": Wonder, Joy, Sweet, and Natural. The group debuted with the release of their first extended play Would You Like? on February 25, 2016. The agency announced their fan club name, Ujung 우정 (friendship) on January 11, 2017.
The first member of Cosmic Girls revealed to the public was SeolA, who had made a cameo in Boyfriend's "Janus" music video in 2012. The second member shown to the public was Dayoung, a former contestant on the music audition television show "K-Pop Star 1." The third member revealed to the public was Dawon, a former contestant on the survival audition show "K-pop Star 2." The fourth member revealed to the public was Exy, a contestant on the female rap competition show "Unpretty Rapstar 2." The fifth member revealed to the public was Eunseo, who had made a cameo in Monsta X's "Rush" music video prior to debut.
On December 1, 2015, Starship Entertainment started to release information about the new girl group through several social media platforms with images of a planet, a heart sign, and a combined orbit and heart. On December 2, Starship Entertainment continued teasing by posting a photo of a silhouette gazing at an orbited heart sign; this image became WJSN's official logo. The first unit, the Wonder unit, was revealed on December 10, consisting of members Cheng Xiao, Bona, and Dayoung. The second unit, the Joy unit, was revealed with members Yeoreum, Eunseo, and Xuan Yi. The third unit, the Sweet unit, was revealed on December 24 with members SeolA, Exy, and Soobin. The final unit, the Natural unit, was released on December 31, consisting of members Mei Qi, Luda, and Dawon, revealing them as a group to the public for the first time.
On December 21, Cosmic Girls released a Christmas cover of Mariah Carey's "All I Want for Christmas Is You" through JuseTV's YouTube Channel.
On January 2, 2016, Dawon, Cheng Xiao, Xuan Yi, Exy, and Eunseo made cameos in UNIQ's New Year's music video. On January 10, 2016, Starship Entertainment started releasing "Play-File" teasers, with a different member's teaser released every day. On January 20, 2016, SeolA, Exy, Bona, Eunseo, Xuan Yi, and Cheng Xiao were featured in Cosmopolitan Korea's February issue in an article entitled "Next Body Icon, Cosmic Girls!"
On February 1, 2016, Eunseo made a cameo in Yoo Seungwoo's "Whatever" music video along with label mates Boyfriend's Jeongmin and Monsta X's Kihyun.
Cosmic Girls debuted on February 25, 2016, with the release of their debut mini-album Would You Like?, including the singles "Mo Mo Mo" and "Catch Me." The music video for "Mo Mo Mo," which features Lee Kwangsoo, was released on February 24, and the music video for "Catch Me" was released on March 9. The group held their debut stage on the February 25th episode of "M Countdown," performing both songs.
On July 11, 2016, Starship Entertainment confirmed that I.O.I.'s Yeonjung would be joining the group. Yeonjung started promoting with the group in August.
In August 2016, Exy, Cheng Xiao, SeolA, Soobin, Eunseo, Yeoreum, and Dayoung teamed up with label mate Monsta X to form the unit "Y-Teen." Y-teen is a project unit group that promotes as CF models for KT’s phone fare service, releasing EPs, music videos, and other entertainment content.
On August 17, 2016, Cosmic Girls released their second mini-album The Secret with all 13 members. The group promoted the title track "Secret."
On January 4, 2017, Cosmic Girls released their third extended play, From. WJSN, with 6 new songs, including the track "I Wish."
On January 11, Starship Entertainment unveiled their official fan club name, Ujung 우정 (friendship).