Sung Jae-ki (; 成在基, 11 September 1967 – 26 July 2013) was a South Korean human- and civil-rights activists, Liberalism thinkers. From 2008 to 2013, he was the first leader of 'Man of Korea' (), a men's rights and men's liberalism civic group. he was abolition activity of ministry of woman. He was early leaders of South Korean Men's liberation movements, In 1999 to 2013, he actively participated in liberalism movement, gender liberation movement, anti-feminist movement until his death.