Introduction <p>Men-who-have-sex-with-men (MSM), as well as transgender and non-binary individuals, continue to face a disproportionate burden of stigma, mental health challenges, HIV, and other sexually transmitted infections. To address their needs, public health planners require reliable and comparable data. Monitoring behaviours in these populations also supports the evaluation of health policies.</p> Methods <p>The European-MSM-Internet-Survey (EMIS-2024) builds on our international surveys conducted in 2010 and 2017, expanding its scope to include explicitly transgender women and non-binary people. It provides much-needed data for planning interventions, promoting health, and harmonising behavioural surveillance. A key strength of EMIS-2024 is the use of a shared sampling frame and a core questionnaire across all participating countries. This approach allows meaningful cross-national comparisons, unlike many national surveys with varying methods. The three core consortium partners (Deutsche Aidshilfe, Robert Koch Institute and Maastricht University) led the revision of the EMIS-2017 questionnaire.</p> Results <p>Over 60 partners from 40 countries played a key role in the survey’s success, providing high-quality translations in 35 languages and actively promoting the survey. National partners ensured the survey’s visibility, credibility, and relevance once dating app advertisements or invitations appeared. The survey ran online during the first half of 2024. Overall, 165,380 responses were received, of which 50,330 qualified for the analytic sample.</p> Conclusions and Policy Implications <p>EMIS-2024 demonstrates that large-scale, multi-country sexual health surveys are feasible with public funding. A harmonised questionnaire, shared sampling strategy, and meaningful community involvement were key to generating robust, comparable data across Europe.</p>