Lee Seung-hwan (born October 12, 1993), known professionally as Seo Kang-joon, is a South Korean actor and former singer, who was a member of the group 5urprise. He gained recognition with his role in the television series Cheese in the Trap (2016) and has since starred in Are You Human? (2018), Watcher (2019), When The Weather Is Fine (2020), Grid (2022), Undercover High School (2025), and Boyfriend on Demand (2026).