Dai, XiaochenNg, MarieGil, Gabriela FernandaMorgan, Brooks W.Anderson, Jason A.Adnani, Qorinah Estiningtyas SakilahAji, BudiAljunid, Syed MohamedAmul, Gianna Gayle HerreraAnwar, Sumadi LukmanApostol, Geminn Louis CaraceArtanti, Kurnia DwiBenjakul, SarunyaBermudez, Amiel Nazer C.Chong, BryanChu, Dinh ToiDo, Thanh ChiEfendi, FerryEffendi, Diyan ErmawanFauk, Nelsensius KlauHargono, AriefHas, Eka Mishbahatul MarahHuynh, Hong HanIndriasih, EndangIqhrammullah, MuhammadJairoun, Ammar AbdulrahmanKanmodi, Kehinde KazeemKhusun, HeldaKurniasari, Maria DyahKusuma, DianLaksono, TriLe, Nhi Huu HanhLe, Thao Thi ThuMa, StefanMarzo, Roy RilleraMohammed, MustaphaMurray, Christopher J.L.Nascimento, Gustavo G.Nguyen, Phat TuanNguyen, Van ThanhNingrum, Dina Nur AnggrainiNoman, Efaq AliO'Connell, Erin M.Ong, Sok KingRoy, BedantaSafi, Sher ZamanSarasmita, Made ArySelvaraj, SiddharthanShrestha, SunilSolikhah, Solikhah2026-07-062026-07-062468-2667PubMed:40441812ORCID:/0000-0002-3930-7021/work/219177182https://hdl.handle.net/1885/733813033Background: Tobacco smoking has long been a regional health priority for the Association of Southeast Asian Nations (ASEAN). Despite decades of commitment to implementing tobacco control measures, the ASEAN region continues to face substantial challenges in reversing the epidemic. We aimed to analyse longitudinal data on smoking prevalence and attributable disease burden to understand the trajectory of the smoking epidemic, inform priority setting, and enable effective policy planning. Methods: We used data from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021 to evaluate the prevalence of tobacco smoking and its attributable disease burden in the ten ASEAN member states by age and sex, from 1990 to 2021. Current smoking prevalence was estimated using spatiotemporal Gaussian process regression models, which synthesised data from 159 distinctive data sources specific to the ASEAN region in addition to 2646 data sources from other GBD countries. Dose–response risks for 36 health outcomes were derived using the latest burden of proof approach. Population attributable fractions were subsequently calculated and applied to determine the burden in terms of mortality, years of life lost, years lived with disability, and disability-adjusted life-years (DALYs) attributable to tobacco smoking in these countries. Findings: In 2021, there were approximately 137 million (95% uncertainty interval 134–139) current smokers aged 15 years and older in the ASEAN region, with an estimated age-standardised prevalence of 48·4% (47·5–49·2) among males and 4·47% (4·09–4·92) among females. Tobacco smoking accounted for 10·8% (8·86–12·9) of all-cause mortality across the region. The total number of deaths and DALYs attributed to smoking were 526 000 deaths (433 000–622 000) and 15·7 million (12·9–18·5) DALYs. Death rates varied considerably across the region, especially among males, ranging from 68·9 (55·8–84·2) per 100 000 males in Singapore to 364 (279–463) per 100 000 males in Cambodia. Although smoking prevalence declined substantially in most ASEAN countries between 1990 and 2021, the absolute number of smokers increased by 63·3% (59·0–67·8), and the number of smokers aged 10 years and older increased by 53·0 million (50·2–56·2). Interpretation: Tobacco smoking remains a persistent public health threat in the ASEAN region. Considerable disparities exist across the region: while some countries have made remarkable progress in tobacco control, others lag behind. As a modifiable risk factor heavily influenced by commercial determinants, smoking can be controlled through effective policy changes. As a geopolitical and economic collaboration network, ASEAN countries must work together to overcome barriers hindering anti-tobacco efforts and collectively devise strategies to strengthen tobacco control across the region. Funding: Bloomberg Philanthropies and the Bill & Melinda Gates Foundation.This study was supported by Bloomberg Philanthropies and the Bill & Melinda Gates Foundation. Editorial note: The Lancet Group takes a neutral position with respect to territorial claims in published maps and institutional affiliations.enPublisher Copyright: © 2025 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license202510.1016/S2468-2667(24)00326-8105006568348