Mirror (stylised in all caps) is a Hong Kong boy group formed through ViuTV's reality talent show Good Night Show - King Maker in 2018. The group consists of twelve members: Frankie Chan, Alton Wong, Lokman Yeung, Stanley Yau, Anson Kong, Jer Lau, Ian Chan, Anson Lo, Jeremy Lee, Edan Lui, Keung To, and Tiger Yau. They debuted on 3 November 2018 with the single "In a Second".

The group has won numerous accolades since their debut, including a Metro Radio Hits Music Award for Best Group, an Ultimate Song Chart Award for Group of the Year (Gold), and Group of the Year (Gold) at the inaugural Chill Club Music Awards held by ViuTV. Mirror is credited for being one of the driving forces in the renewed interest of the Cantopop genre and to have prompted an unprecedented wave of fandom culture in Hong Kong. Their 2020 single "Ignited" won Top Ten Song of the Year at the Ultimate Song Chart Awards and the Chill Club Music Awards. Their 2021 single "Warrior" topped the Ultimate 903 Chart for two weeks, the first song from a group to do so in 15 years.

All members of Mirror have also debuted individually and participated in various drama series, reality shows, and films.

In July 2018, ViuTV's reality talent competition Good Night Show - King Maker started scouting for potential artistes. 99 male contestants successfully auditioned for the show. Participants performed individually and in groups, with a panel of judges deciding who would advance to the next round. The finale aired live on 14 October 2018, with results decided by a public vote and a judging panel. Keung To won the competition, with Ian in second place, and Lokman in third. Anson Kong, Edan, Jeremy, and Stanley were among the top 10. ViuTV intended to form a boy group with the top 10 finalists and proceeded with contract talks.

Mirror officially debuted on 3 November 2018 with twelve members, with King Maker's producer, Ahfa Wong as the group's manager. According to the group's leader, Lokman, the name Mirror was chosen because "members look in the mirror every morning and see their real selves; when there are multiple mirrors, they can reflect infinite images; similarly, with infinite potential, the combination of these unique members would allow for unlimited possibilities." During the debut press conference, they performed their debut single "In a Second" (Chinese: 一秒間).

On 21 December 2018, they held their first live concert, the 2018 First Mirror Live Concert, at the Kowloonbay International Trade & Exhibition Centre Star Hall. The tickets were sold from 15 November 2018 and all tickets were sold out. During the concert, apart from performing some original songs, they also performed Korean pop songs including "Love Song" and "Trouble Maker", although they expressed their preference of creating their unique renditions instead of going for a "K-pop feel".

Between January 2019 and November 2020, the group released five more singles, including "ASAP" (2019), "Broken Mirror" (破鏡) (2019), first-year anniversary single "Reflection" (2019), "Ignited" (2020) and "One and All" (2020). "Ignited" won two awards at Hong Kong's major year-end music awards shows, including the Ultimate Song Chart Awards and the inaugural Chill Club Awards.

Members also began to make their solo debuts, with Ian and Keung To in 2019, and Anson Kong, Anson Lo, and Jer in 2020.