Ryu Seung-ryong is a South Korean actor. Ryu began his acting career in theater, subsequently becoming one of the most versatile supporting actors in Korean film and television. In 2013, he headlined Miracle in Cell No. 7, which became the third highest grossing Korean film of all time, in 2014 he starred in historical film The Admiral: Roaring Currents, which is currently the highest-grossing film of all time in South Korea, and in 2019 he headlined the comedy film Extreme Job, which is currently the 2nd highest-grossing film of all time in South Korea. Ryu is the first Korean to star in four movies that have drawn over 10 million viewers each.

Miracle in Cell No. 7 is a 2013 South Korean comedy drama film starring Ryu Seung-ryong, Kal So-won and Park Shin-hye. The film is about a developmentally disabled man wrongfully imprisoned for murder, who builds friendships with the hardened criminals in his cell, who in return help him see his daughter again by smuggling her into the prison.