Kim Sung-kyu (born April 28, 1989), referred to as Sunggyu or Sungkyu, is a South Korean singer and actor. He is the leader and main vocalist of South Korean boy band Infinite.

In November 2012, Sungkyu began his solo career with his first extended play, Another Me, debuted at number one on the Gaon Album Chart. He continued to release a second extended play, 27 (2015), debuted at number one on the Gaon Album Chart and number eight on The Billboard World Album, and yielded two South Korean top-ten singles "The Answer" and "Kontrol".