Consuming products that contain smokeless tobacco or areca nut increases the risk of oral cancer. We aimed to estimate the burden of oral cancer attributable to smokeless tobacco or areca nut consumption globally and by type of smokeless tobacco or areca nut product in four major consuming countries. We calculated population attributable fractions (PAFs) using prevalence of current use of smokeless tobacco or areca nut products from national surveys and corresponding risks of oral cancer from the literature. We applied PAFs to national estimates of oral cancer incidence in 2022 from the Global Cancer Observatory's Cancer Today database to obtain cases attributable to smokeless tobacco or areca nut consumption. We modelled 95% uncertainty intervals (UIs) using Monte Carlo simulations. Globally, an estimated 120 200 (95% UI 115 300-124 300) cases of oral cancer diagnosed in 2022 were attributable to smokeless tobacco or areca nut consumption, accounting for 30·8% (95% UI 29·6-31·9) of all oral cancer cases (120 200 of 389 800). An estimated 77% of attributable cases were among male patients (92 600 cases, 95% UI 88 000-96 500) and 23% were among female patients (27 600 cases, 26 000-29 000). Regions with the highest PAFs were Melanesia, Micronesia, and Polynesia (78·6%, 95% UI 74·4-80·5), southcentral Asia (57·5%, 54·8-59·5), and southeastern Asia (19·8%, 19·0-20·6). Lower-middle-income countries represented 90·2% of the world total attributable cases (108 400 cases, 95% UI 103 400-112 200). Our findings suggest that one in three cases of oral cancer globally are attributable to smokeless tobacco or areca nut consumption, and could be prevented through smokeless tobacco and areca nut control. Global cancer control efforts must incorporate further measures to reduce smokeless tobacco and areca nut consumption in populations with the largest attributable burden. French National Cancer Institute.