BACKGROUND: Headache disorders, including migraines and tension-type headaches (TTH), are major contributors to global disability. In South Asia, where these conditions are often underdiagnosed, their burden has grown substantially. This study evaluates trends in headache disorders across eight South Asian countries from 1990 to 2021, using data from the Global Burden of Disease (GBD) Study 2021. METHODS: Data from the GBD study were analysed to evaluate incidence, prevalence, and years lived with disability (YLDs) for headache disorders and their subtypes. Trends were assessed using absolute numbers and age-standardized rates, with demographic patterns by age and gender examined to identify vulnerable populations. Joinpoint regression analysis was employed to detect significant temporal shifts. RESULTS: From 1990 to 2021, headache disorders in South Asia rose from 114.2 million to 206.8 million in incidence, and from 367.4 million to 698.5 million in prevalence, with YLDs nearly doubling from 6.0 million to 11.6 million. Migraines accounted for 294.4 million cases, while TTH contributed 495.4 million cases, with YLDs increasing by 92.88 and 99.35%, respectively. Afghanistan saw the highest relative growth, while India contributed the largest absolute burden. Women and middle-aged adults were disproportionately affected, with the highest prevalence observed in females aged 30-34 years. The Maldives showed dramatic increases in TTH-related YLDs, highlighting disparities in smaller nations. CONCLUSION: The rising burden of headache disorders in South Asia highlights the need for region-specific strategies targeting high-burden subtypes, countries, and vulnerable populations to mitigate their disabling impacts.