The anti-gender movement is an international movement against "gender ideology", "gender theory", or "genderism". The anti-gender movement rejects the sex and gender distinction, arguing that any gender separate from biological sex should not be recognized. Anti-gender advocates often oppose changes to the traditional family, such as same-gender marriage. Advocates of the anti-gender movement take issue with femininity in men, masculinity in women, and the existence of trans and non-binary people.
The anti-gender movement originated in 1990s specifically within the Catholic Church. They began to counter the results of the United Nations' 1994 International Conference on Population and Development and the 1995 World Conference on Women. The Holy See feared that this recognition would lead to abortion, delegitimization of motherhood, and the normalization of homosexuality. The term gender "was understood by the Holy See as a strategic means to attack and destabilize the natural family".
In 1997, American anti-abortion journalist Dale O’Leary wrote a book titled The Gender Agenda: "the Gender Agenda sails into communities not as a tall ship, but as a submarine, determined to reveal as little of itself as possible". In Catholic thought, the concept of "gender ideology" emerged from John Paul II's theology of the body, in which the sexes are held to be different and complementary. Although the ideas of the anti-gender movement were developed by 2003, protests related to the movement first emerged in most European countries around 2012–2013. Although it is still promoted by Catholic actors, the anti-gender movement spread more generally throughout the right-wing by 2019.