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 [albumartist=X1]Quantum Leap. They were supposed to be active for five years, however after investigations regarding Mnet's voting manipulation in the Produce 101 series, the members' agencies could not agree on a contract so that the group disbanded on January 6, 2020.