"Fly High X1! Hello, we are X1!" X1 (엑스원) was an 11-member project boy group under Swing Entertainment and Stone Music Entertainment. They were formed through Mnet's competition reality show Produce X 101 and debuted on August 27, 2019 with their first mini album 비상 : Quantum Leap.
The group disbanded on January 6, 2020 after the agencies representing the members could not reach an unanimous agreement following the Produce 101 vote manipulation controversy.
They were intended to be active for five years on a special contract, where the first semester is intended for them to focus solely on the group, and in the second half they will be able to do work within their own companies, such as solo debut, a member of a new group or returning to work with a former group.
Following the conclusion of Produce X 101, vote rigging allegations surfaced after viewers noticed irregularities in the number of votes counted, which series PD Ahn Joon Young later admitted were rigged. Despite of this at the time, their debut moved forward.
A reality show titled X1 Flash, which followed their process to debut, began airing on August 22. X1 debuted on August 27 with the release of their first mini album 비상 : Quantum Leap and held their debut show-con at the Gocheok Sky Dome in Seoul.
By November 2019, the group had temporarily halted all activities due to the severity of the event. It was also revealed that some members had still not yet signed contracts with CJ ENM due to the ongoing investigation.
On December 30, CJ ENM's CEO Heo Min Heoi held a press conference to make a formal apology regarding the manipulation controversy surrounding the Produce 101 series. He explained that CJ ENM will be compensating everyone harmed due to the incident. Regarding IZ*ONE and X1, he shared that they are working on plans for the groups to resume activities, and Mnet will give up all resulting profits towards a fund.
On January 6, 2020, the agencies representing the members announced the group has disbanded due to not being able to reach an unanimous agreement.