Ong Seong-wu (born August 25, 1995) is a South Korean singer and actor. He is known for his participation in the survival reality show Produce 101 Season 2, where he finished in fifth place, and is a former member of the show's derivative boy group Wanna One. Following Wanna One's disbandment, Ong made his acting debut with the drama At Eighteen (2019) directed by Shim Na-yeon. He also established his career as a solo artist with the release of his first extended play, Layers, on March 25, 2020.