Jung Ki-yeol (born December 5, 1981), known professionally as Kai, is a South Korean singer and musical theatre actor. He is a classically-trained baritone best known in musical theatre and has starred in Korean productions of A Tale of Two Cities, The Three Musketeers and Phantom. Outside of musical theatre, Kai has appeared as a panelist on various singing variety shows such as King of Mask Singer and was host of the classical music show 세상의 모든 음악 (Music of the World) on KBS Classic FM.