Hong Sung-mu (Korean: ???, born 1 January 1942) is a North Korean nuclear weapons scientist and a Workers' Party of Korea (WPK) official working with North Korea's weapons of mass destruction and space programs.
He is the deputy director of the party's Machine Building Industry Department (MBID) and plays a key part in the country's nuclear weapons program.
Hong rose to prominence after the 2011 death of Kim Jong-il and succession of Kim Jong-un, after which he has supervised various weapons tests, including the 2013 and January 2016 North Korean nuclear tests.
Hong's involvement in weapons development has landed him on international sanctions lists.