4B or "Four Nos" is a radical feminist[1] movement that originated in South Korea. The name refers to its defining four tenets which all start with the Korean-language term bi (Korean: 비; Hanja: 非), roughly meaning "no".[2] Its proponents do not date men, marry men, have sex with men, or have children with men.[3] The movement emerged between 2017 and 2019[4][5] on Twitter[6] and on the website WOMAD. It has since spread internationally, namely to the United States after its 2024 presidential election.
The movement is considered fringe in South Korea, and has since declined. Estimates of the movement's adherents vary; reportedly several articles claimed around 5,000 and one article claimed 50,000.[7] In South Korea, a portion of its members, particularly those associated with the openly misandric[8]WOMAD, were described as transphobic and homophobic towards gay men.[9]