Genspect is an international gender-critical anti-trans group founded in June 2021 by psychotherapist Stella O'Malley. Genspect opposes gender-affirming care, as well as social and medical transition for transgender people. Genspect opposes allowing transgender people under 25 years old to transition, and opposes laws that would ban conversion therapy on the basis of gender identity. Genspect also endorses the unproven concept of rapid-onset gender dysphoria (ROGD), which proposes a subclass of gender dysphoria caused by peer influence and social contagion. ROGD has been rejected by major medical organisations due to its lack of evidence and likelihood to cause harm by stigmatizing gender-affirming care.

Genspect's positions contradict major medical organizations such as the World Professional Association for Transgender Health (WPATH), the Endocrine Society, the American Psychiatric Association, American Psychological Association, and the American Academy of Pediatrics, the latter of which states "robust evidence demonstrates that access to gender-affirming care decreases risk of suicidal ideations, improves mental health, and improves the overall health and well-being of transgender and gender-diverse youth".

Genspect is closely affiliated with the Society for Evidence-Based Gender Medicine (SEGM): Seven advisors for SEGM are on Genspect's team or advisors, including founder O'Malley. Genspect consists of parents, educators, counsellors, clinicians, and well-known detransitioners. The Southern Poverty Law Center has designated Genspect and SEGM as anti-LGBTQ hate groups since 2023.

While Genspect positions itself as a "moderate, evidence-based coalition of concerned parents and clinicians", leaked chat logs from a community Discord server operated by Genspect revealed members openly using far-right language such as calling trans people "groomers", "pedophiles" and "a cult" and promoting conspiracy theories such as claiming that being transgender is caused by using social media, watching porn, watching anime and participating in cosplay as well as voicing support for Jennifer Bilek, an influential anti-trans activist in the U.K. who believes Jewish billionaires are funding trans-affirming surgery worldwide as part of a "transhumanist project to abandon the body entirely". Members were also caught comparing gender-affirming care to lobotomies and opioids as well as saying that the transgender movement is operated by "autogynephilic and pedophilic men" who are taking advantage of "changes in society that suit the pursuit of their fetishes".

In June 2021, the conservative British newspaper The Daily Telegraph featured an article marking the launch of Genspect. Stella O'Malley said parents were shocked that gender-questioning children were prescribed drugs "within weeks" of attending a clinic. The NHS disputed the claim, saying access to gender-affirming care was normally a "lengthy process". O'Malley stated "We think that the affirmative approach is too narrow and it is not taking into account co-morbidities, such as autism, or trauma". At the launch, a mother spoke to the Telegraph, claiming that her transgender daughter was "groomed" at school and online into taking hormone treatment. Her daughter had come out to her as a trans girl at 14 years old, asked for puberty blockers at 16, which she refused, and was prescribed hormones from the NHS at 19.

In August 2021, they intervened in a case against the school district in the town of Rhondda Cynon Taf in South Wales for using a student's preferred pronouns in school without the parent's knowledge. Genspect has publicly supported numerous legal complaints against clinicians and has supported parents in efforts to prevent students socially transitioning at school against parent's wishes. Genspect has advised parents and schools against using transgender children's chosen names and pronouns and recommended schools ban tucking and chest binding.

Genspect has also campaigned against access to gender transition for those under age 25. On the subject of gender-affirming care for people over 25, Genspect's vice director, Alasdair Gunn claimed that their focus on youth transition is a political strategy to reach left-leaning voters in order to eventually push for restrictions on transitioning for people of all ages. Gunn clarified that, "None of us would ever recommend transition for anyone. On those over 25 we say little, because it's not in YOUR interests to mention this. We have to break through to the policymakers who are left of center, and the way to do that is to focus relentlessly on the problem of transition for under 25s."

Genspect promoted misinformation about Boston Children's Hospital, claiming they perform vaginoplasties on minors. However, no such surgeries were performed. Genspect did not apologize, instead claiming that adolescence lasts until 25 years old, so therefore the hospital was performing surgeries on "adolescents".