The Health Behaviour in School-aged Children (HBSC) study is a large school-based survey carried out every four years in collaboration with the WHO Regional Office for Europe. HBSC data are used at national/regional and international levels to gain new insights into adolescent health and well-being, understand the social determinants of health and inform policy and practice to improve young people’s lives. The 2021/2022 HBSC survey data are accompanied by a series of volumes that summarize the key findings around specific health topics. This report, Volume 5 in the series, focuses on adolescent sexual health, using the unique HBSC evidence on the sexual health of adolescents aged 15 years across 42 countries and regions in Europe, Central Asia and Canada (two of the 44 countries and regions in the study could not collect data on sexual behaviours). It describes the current sexual health status of adolescents by analysing their sexual initiation, contraceptive pill and condom use (or non-use) at last sexual intercourse, the role of gender, age and social inequality, and how adolescent sexual behaviour has changed over time. Findings from the 2021/2022 HBSC survey provide an important evidence benchmark for current research, intervention and policy-planning.