The group has nine members: Mimi, Hana, Haebin, Nayoung, Sejeong, Sally, Soyee, Mina, Hyeyeon. Three members - Nayoung, Sejeong, and Mina - participated in the first season of Produce101. Because they were in the final 11, Sejeong and Mina debuted in I.O.I.
gu9udan debuted on June 28, 2016 with the single 'Wonderland' and the mini-album 'Act. 1 The Little Mermaid'.
Their first subunit 'gugudan 5959' or 'gugudan Ogu-ogu' - which consisted of their two youngest members - debuted August 10, 2017 with the single 'Ice Chu'.
Another subunit 'SEMINA' - Sejeong, Nayoung, Mina - debuted July 10, 2018 with 'SAEMINA', the subunit name being made up of the first syllables of their names.
- Mimi (Jung Mimi, born January 1, 1993)
- Hana (Shin Bora, born April 30, 1993)
- Haebin (Han Haebin, born August 16, 1995)
- Nayoung (Kim Nayoung, born Novemver 23, 1995)
- Sejeong (Kim Sejeong, born August 28, 1996)
- Sally (Liu Xie Ning/Ryu Sajeonote , born October 23, 1996)
- Soyee (Jang Sojin, born November 21, 1996)
- Mina (Kang Mina, born December 4, 1999)
- Hyeyeon (Cho Hyeyeon], born August 5, 2000)
Members in gugudan 5959:
Members in guguda SEMINA:
- Act. 1 The Little Mermaid - Jun. 28, 2016
- Act. 2 Narcissus - Feb. 27, 2017
- Act. 3 Chococo Factory - Nov. 8, 2017
- Act. 4 Cait Sith - Feb. 1, 2018
Tropes Related to gu9udan:
- Aerith and Bob: Mimi, Hana, Haebin, Nayoung, Sejeong, Soyee, Mina, Hyeyeon and Sally.
- all lowercase letters: How 'gugudan' is usually written.
- Chronological Album Title: Act. 1 The Little Mermaid, Act. 2 Narcissus, Act. 3 Chococo Factory, Act. 4 Cait Sith.
- Fan Community Nickname: Dan-jjakn (Dear Friend).
- Girl Group: A Korean Pop Music example.
- The Leader: Hana.
- Letters 2 Numbers: '9' to replace a 'g' in 'gu9udan'.
- One-Word Title:
- 'Diary' and 'Wonderland' in Act. 1 The Little Mermaid
- 'Rainbow' in Act. 2 Narcissus
- 'Chococo', 'Lucky', and 'Snowball' in Act. 3 Chococo Factory
- 'Silly' and 'Lovesick' in Act. 4 Cait Sith
- Stage Names:
- Hana for Bo Ra
- Sally for Xiu Ning/Sa Jeo
- Soyee for So Jin
- Team Mom: Haebin is said to be the "mother of the group".