Pre-debut: Youth With You 2

The9 was formed through the reality television show Youth with You 2, which aired from March 12 to May 30, 2020. It was the third season of the Idol Producer franchise. Out of 109 trainees from different companies, only the top 9 most voted trainees in the final episode got to debut in the final group.

On May 30, 2020, the final lineup was eventually announced. Liu Yuxin placed 1st, Esther Yu Shuxin came in 2nd, followed by Kiki Xu Jiaqi, Yu Yan, Shaking Chloe Xie Keyin, Babymonster An Qi, Zhao Xiaotang, Snow Kong Xue'er, and K Lu Keran in 9th place respectively. Since having earned 1st place, XIN Liu Yuxin was chosen as the center of the group.^[5][6]

2020: Beginning of promotions, debut with Sphinx X Mystery and MatriX

On May 30, 2020, The9 was formed following the finale of Youth with You Season 2 and their training began the day after. Apart from training, they also filmed for several variety shows such as "My Little Forest". On June 17, 2020, they participated in Hunan Television's 618 Super Night to perform "Yes! OK!" and "Hunt", marking The9's first public performance. On July 4, 2020, the official Weibo account for the group released a video of the members selecting their team leader, revealing to be Babymonster An. They also revealed other details such as their fandom name, fandom colors as well as their hand sign.

On July 10, 2020, the group attended the "Current Business Conference" and announced their appointment as "Advance Officer for Edge Art."^[7]

The group has also done many commercials as well as editorials for magazines and high-end fashion houses. Xu Jiaqi, a former member of Chinese girl group SNH48's Team SII as well as a current member of the SNH48 sub-unit 7Senses, performed at SNH48's 7th Request Time Senbatsu General Elections as a guest.

The group released their first extended play, Sphinx X Mystery (斯芬克斯X谜), on August 10, 2020.^[8] The EP consists of the lead single "SphinX" (斯芬克斯) as well as another song titled "Not Me". The EP sold over 150,000 units in less than 45 minutes; it also won the "Double Platinum" rating.^[9] The music video for SphinX was released on August 15 via Weibo and YouTube. They promoted their EP through performances at variety shows and through music shows such as 818 Super Night. The group then announced their first variety show called “Let’s Party 2020” which would be released on iQIYI. The group released their debut studio album MatriX (虚实X境) on December 25, 2020^[10] which features the lead single "Dumb Dumb Bomb" and nine solo tracks.

On December 31, The9 participated in the 2021 Jiangsu Satellite TV New Year's Eve concert.^[11]

2021: RefleXtion, THE NINE and disbandment

From March 26–27, 2021, The9 held their first online concert titled "X-CITY," which garnered tens of thousands of viewers. The concert utilized XR technology to create realistic stage backgrounds.^[12]

On June 9, 2021, the group released their first anniversary EP entitled RefleXtion. The EP consists of two tracks: "Hello" and "Xenogeneic". The group officially disbanded on December 5, 2021.^{[citation needed]} Though the group had plans to hold a graduation concert, due to the COVID-19 pandemic, these shows have been indefinitely halted.^{[citation needed]}

2022–2023: Reunion concerts

On August 19–20, 2022, The9 held their first reunion concert since disbandment at the Harbin International Convention Exhibition and Sports Center.^[13]

On October 27–28, 2023, the group held their second reunion concert at the Nanjing Youth Olympic Sports Park.^[14][15]

Studio albums

Extended plays

Songs

Promotional singles

Music videos

Variety Shows