The King of Mask Singer ^[1] (Korean: 미스터리 음악쇼 복면가왕; RR: Miseuteori Eumaksyo Bongmyeon-gawang; lit. Mystery Music Show: Masked Singer's King) is a South Korean singing competition program presented by Kim Sung-joo,^[2] with introductions by voice actor Lee Won-joon [ko].^[3] It airs on MBC on Sunday, starting from April 5, 2015^[2] as a part of MBC's Sunday Night programming block.^[4]

Each competition lasts for two episodes, with the singers competing one-on-one in three elimination rounds. They are given elaborate masks which are made by designer Hwang Jae-geun [ko]^[5] and gloves to wear in order to conceal their identity, thus removing factors such as popularity, career and age that could lead to prejudiced voting. In the first round, both contestants sing the same song, while in the second and third round they each sing a solo song. The winners of each pair are selected by the audience and panel of celebrities through instant live votes. The identities of the singers are not revealed until they have been eliminated.^[6] The winner of the third round challenges the previous competition's Mask King, and is either eliminated or becomes the new Mask King.^[7] Ha Hyun-woo of Guckkasten ("Music Captain of Our Local") has nine consecutive wins, which is the highest number of wins achieved by any contestant (and highest number of males)^[8][9] and Son Seung-yeon ("The East Invincibility") has eight consecutive wins, which is the highest number of consecutive wins ever achieved by a female contestant.

Due to great interest and demand, the show released a special album consisting of a selection of studio recordings by the competitors.

List of idol contestants performed in this show, include the ex-idols and exclude the sub-groups (initial sort by group)

  – Idol group has been disbanded

  – Idol group is on hiatus

(The contestant's names in bold are the male and female Mask King with the most wins.)

(The bold winner is the contestant who became the Mask King.)