Loona (stylized in all caps or as LOOΠΔ; Korean: 이달의 소녀; RR: Idarui Sonyeo; Japanese: 今月の少女, romanized: Kongetsu no Shōjo, lit. 'Girl of the Month') is a South Korean girl group formerly under Blockberry Creative. The group is composed of eleven members: Heejin, Hyunjin, Haseul, Vivi, Yeojin, Kim Lip, Jinsoul, Choerry, Yves, Go Won, and HyeJu (formerly Olivia Hye). Originally a twelve-member group, Chuu was removed from the line-up on November 25, 2022, due to a contract dispute. Starting in October 2016, as part of a pre-debut project, each member was introduced to the public through a solo promotional single over the following 18 months in a periodic fashion. The group debuted as a full ensemble on August 19, 2018, with the extended play (EP) [+ +], supported by the lead single "Favorite" and the title track "Hi High".

On November 28, 2022, JTBC reported that all of the remaining members, excluding Hyunjin and Vivi, had filed for provisional injunction to suspend their contracts with Blockberry Creative. On January 13, 2023, HeeJin, Kim Lip, JinSoul, and Choerry were granted preliminary injunctions, and they subsequently signed with Modhaus on March 17. On May 9, HyunJin and ViVi were granted preliminary injunctions, and both members signed with CTDENM two days later. On June 16, Seoul Economic Daily reported that the remaining members had won the lawsuit against the label, terminating their contracts. On June 21, it was announced that Haseul had signed with Modhaus. On July 5, it was reported that YeoJin, Go Won and HyeJu had signed with CTDENM. On July 6, Yves revealed she would continue as a soloist.