Background: Reports from several high-income countries have demonstrated a rising incidence of oral tongue cancer (OTC) among younger adults. However, objective, subsite-specific, global incidence data is lacking. This study aimed to investigate OTC incidence trends in younger and older adults globally as well as sex differences among groups.Methods: Data on OTC incident cases were derived from the IARC Cancer Incidence in Five Continents Detailed Volumes X-XII (2003-17). Only registries reporting in all three volumes with a stable covered population were included. Populations were stratified by age, particularly under 45 (early-onset OTC (EO-OTC)) and 45 or older (average-onset OTC). Age-standardized incidence rates were pooled and derived from 2008-2017 for each country. Average period change was estimated by age- and sex-adjusted quasi-Poisson regressions. Countries were compared as paired observations by Wilcoxon signed rank tests.Findings: A total of 17,374 EO and 142,992 average-onset OTC cases were recorded. Nine of the 10 countries with the highest incidence were designated as high-income countries (HICs). Nine of the 45 countries included showed significant EO increases. Increases in incidence in EO trends exceeded increases in average-onset OTC incidence in 30 of 45 countries. Oral tongue was the leading subsite within the OCC (+11.6% per period). Results by sex demonstrated that trends in females exceeded those in males in 29 of 42 countries (p=0.039) for early-onset and in 36 of 45 in average onset (p < 0.0001).Interpretation: EO-OTC is rising globally, with a disproportionate increase in HICs. The oral tongue contributes the majority of incident cases in the OCC and demonstrates the steepest rise of any subsite. The OTC incident shift is female-predominant, regardless of income status, and raises hypotheses about distinct driving etiopathologies.