Song Jeong-sik (; born December 11, 1983), better known by his stage name On Joo-wan, is a South Korean actor. He won widespread praise for his leading role in the film The Peter Pan Formula, and also appeared in My Mighty Princess, 12 Signs of Love, and The Five.
On July 4, 2025, it was announced that On would marry his Beautiful Gong Shim co-star Bang Min-ah after dating for four years. The couple married on November 29, 2025, in Bali.