Conversion therapy is the pseudoscientific practice of attempting to change an individual's sexual orientation, gender identity, or gender expression to align with heterosexual and cisgender norms. Methods that have been used to this end include forms of brain surgery, surgical or hormonal castration, aversive treatments such as electric shocks, nausea-inducing drugs, hypnosis, counseling, spiritual interventions, visualization, psychoanalysis, and masturbatory reconditioning.

There is a scientific consensus that conversion therapy is ineffective at changing a person's sexual orientation or gender identity and that it frequently causes significant, long-term psychological harm in individuals who undergo it. The position of current evidence-based medicine and clinical guidance is that homosexuality, bisexuality and gender variance are natural and healthy aspects of human sexuality. Historically, conversion therapy was the treatment of choice for individuals who disclosed same-sex attractions or exhibited gender nonconformity, which were formerly assumed to be pathologies by the medical establishment.

An increasing number of jurisdictions around the world have passed laws against conversion therapy. Conversion therapy may constitute fraud and when performed on minors, a form of child abuse; it has been described by experts as torture, cruel, inhuman, or degrading treatment, and contrary to human rights.