Background: Gambling behaviours have become of increased public health interest, but data on prevalence remain scarce. In this study, we aimed to estimate for adults and adolescents the prevalence of any gambling activity, the prevalence of engaging in specific gambling activities, the prevalence of any risk gambling and problematic gambling, and the prevalence of any risk and problematic gambling by gambling activity., Methods: We performed a systematic review and meta-analysis. We systematically searched for peer-reviewed literature (on MEDLINE, Embase, and PsycInfo) and grey literature to identify papers published between Jan 1, 2010, and March 4, 2024. We searched for any gambling, including engagement with individual gambling activities, and problematic gambling data among adults and adolescents. We included papers that reported the prevalence or proportion of a gambling outcome of interest. We excluded papers of non-original data or based on a biased sample. Data were extracted into a bespoke Microsoft Access database, with the Joanna Briggs Institute Critical Appraisal Tool used to identify the risk of bias for each sample. Representative population survey estimates were firstly meta-analysed into country-level prevalence estimates, using metaprop, of any gambling, any risk gambling, problematic gambling, and by gambling activity. Secondly, population-weighted regional-level and global estimates were generated for any gambling, any risk gambling, problematic gambling, and specific gambling activity. This review is registered on PROSPERO (CRD42021251835)., Findings: We screened 3692 reports, with 380 representative unique samples, in 68 countries and territories. Overall, the included samples consisted of slightly more men or male individuals, with a mean age of 29·72 years, and most samples identified were from high-income countries. Of these samples, 366 were included in the meta-analysis. Globally, 46·2% (95% CI 41·7-50·8) of adults and 17·9% (14·8-21·2) of adolescents had gambled in the past 12 months. Rates of gambling were higher among men (49·1%; 45·5-52·6) than women (37·4%; 32·0-42·5). Among adults, 8·7% (6·6-11·3) were classified as engaging in any risk gambling, and 1·41% (1·06-1·84) were engaging in problematic gambling. Among adults, rates of problematic gambling were greatest among online casino or slots gambling (15·8%; 10·7-21·6). There were few data reported on any risk and problematic gambling among adolescent samples., Interpretation: Existing evidence suggests that gambling is prevalent globally, that a substantial proportion of the population engage in problematic gambling, and that rates of problematic gambling are greatest among those gambling on online formats. Given the growth of the online gambling industry and the association between gambling and a range of public health harms, governments need to give greater attention to the strict regulation and monitoring of gambling globally., Funding: Australian National Health and Medical Research Council., Competing Interests: Declaration of interests In the last 5 years, HW has received grant funding for gambling-related research from The Economic and Social Research Council, National Institute for Health Research, Wellcome Trust, the Gambling Commission (including their regulatory settlement fund), Office of Health Disparities and Improvements and Public Health England, Greater London Authority, Greater Manchester Combined Authority, Blackburn with Darwen Local Authority, and the Department of Digital Culture Media and Sport; received funding from GambleAware in 2018–19 for a project on gambling and suicide; received consulting fees from the Institute of Public Health, Ireland, and the National Institute for Economic and Social Research; received payment for the delivery of seminars from McGill University, the University of Birmingham, Johns Hopkins University, and from the British Broadcasting Corporation; has been paid as an expert witness by Lambeth and Middlesbrough Borough Councils; has received travel costs paid by Gambling Regulators European Forum, the Turkish Green Crescent Society, Alberta Gambling Research Institute, the REITOX Academy (administered through the Austrian National Public Health Institute), and the University of Helsinki; served as the Deputy Chair of the Advisory Board for Safer Gambling between 2015 and 2020, remunerated by the Gambling Commission; is a member of the WHO panel on gambling (ongoing); provided unpaid advice on research to GamCare for their Safer Gambling Standard (until mid-2021); runs a research consultancy for public and third sector bodies only, but has not, and does not, provide consultancy services to gambling industry actors; in researching the gambling industry and their practices, has occasionally attended events where gambling industry actors are present (including industry-sponsored conferences); and as part of her work on the Gambling Survey for Great Britain, is required by the Gambling Commission (the funder) to participate in events disseminating research findings to their stakeholders, which includes the industry, but is independently funded and does not involve collaborations or partnerships with industry. VM has received grant funding for gambling-related projects from the Academy of Finland (project numbers 349589 and 31834), the Finnish Ministry of Social Affairs and Health, and the Finnish Ministry of Justice; as a member of the Gambling Harms Evaluation Committee (2021 onwards) and the Indicators for Gambling Harms work group (2019–21) under the Finnish Ministry of Social Affairs and Health, she interacts with the Finnish gambling monopoly to evaluate company products and practices and to analyse company data; has received a fee for delivering a webinar from Bochum University; did a paid peer review for Routledge; received funding for travel from the Finnish Foundation for Alcohol Studies, University of Bergen, and the Council of Europe; and provides consultation for public and third sector actors, but not the gambling industry. CB has received grant funding for gambling-related projects from The British Academy, The Economic and Social Research Council, the National Institute of Health Research, Blackburn with Darwen Local Authority, and the Department for Culture, Media and Sport. RV has received grant funding for gambling-related projects from the Massachusetts Gaming Commission, the Connecticut Department of Mental Health & Addiction Services, the Evergreen Council for Problem Gambling, The University of Massachusetts Donahue Institute, Gambling Research Exchange Ontario, NORC Boston, North Dakota Department of Health & Human Services, British Gambling Commission, Public Health Agency of Sweden, Canadian Centre on Substance Abuse, and the Center for Gambling Studies, Rutgers University; has received consultancy fees for gambling-related research from the National Centre for Social Research UK, Gambling Research Exchange Ontario, and the Karolinska Institute; has received honorarium from McGill University for the delivery of a webinar, from the Evergreen Council on Problem Gambling, the Institut für Glücksspiel und Gesellschaft, and the New York State Council on Problem Gambling; and has received travel costs from the Alberta Gambling Research Institute in 2022 and 2023 and from the Nigerian National Lotteries Regulatory Commission in 2023. JR has received funding from various national and international public funding agencies (the Canadian Institutes of Health Research, US National Institutes of Health, the EU, and WHO); and funding for travel from WHO. In the past 5 years, LD and MF have received untied educational grant funding from Indivior and Seqirus for the study of new opioid medications in Australia. SS has been a senior advisor to the McKinsey Health Institute since 2023 for issues on mental health. All other authors declare no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY-NC-ND 4.0 license. Published by Elsevier Ltd.. All rights reserved.)