Background: Atrial fibrillation and flutter (AF/AFL) represent a major global public health challenge, contributing significantly to stroke, heart failure, and cardiovascular mortality. While previous studies have documented a rising AF/AFL burden, comprehensive comparisons of long-term trends and forecasts across regions—particularly benchmarking China against Southeast Asia, Europe, and global averages—remain limited. This study aims to quantify the AF/AFL burden across these regions from 1990 to 2021 and project trends to 2050. Methods: Using data from the Global Burden of Disease Study 2021, we analysed the burden of AF/AFL from 1990 to 2021 in China, Southeast Asia, Europe, and globally. We examined incidence, prevalence, mortality, and disability-adjusted life years (DALYs). Advanced analytical methods, including Joinpoint regression, age-period-cohort modelling, decomposition analysis, Frontier analysis and Bayesian forecasting were employed to assess trends, drivers, and projections to 2050. Finding: From 1990 to 2021, China experienced the most rapid increase in age-standardized incidence rate (ASIR) globally (AAPC +0.16%), with incident cases rising to 916,180, accounting for 20.43% of the global total. In contrast, Europe saw a slight decline in ASIR, while the global ASIR remained stable. China also recorded the largest increase in age-standardized prevalence rate (ASPR), whereas Europe’s ASPR declined. Despite rising incidence, China achieved the sharpest reduction in age-standardized mortality rate (ASMR; AAPC −0.45%), while Southeast Asia’s ASMR increased (AAPC +0.76%), and Europe maintained the highest ASMR globally. Frontier analysis highlighted China’s rapid efficiency improvements in mortality reduction relative to its SDI, outperforming several high-income European countries. Projections to 2050 suggest China’s ASIR and ASPR will continue to rise, whereas Europe’s are forecast to decline. Southeast Asia faces persistently increasing mortality, and global aggregates mask significant regional heterogeneity. Conclusion: AF/AFL burdens are increasingly driven by population aging and metabolic risks, with heterogeneous mortality trends reflecting regional disparities in healthcare access and prevention. China’ s success in reducing mortality despite rising incidence highlights the impact of improved anticoagulation and stroke prevention, yet unchecked prevalence growth signals future complications. Southeast Asia’ s rising mortality underscores urgent needs for equitable resource allocation, while Europe’s stagnant burden reflects challenges in aging populations. Globally, prioritising primordial prevention—such as metabolic risk control—alongside targeted screening and gender-specific interventions, is critical to mitigating AF/AFL-related morbidity and mortality. Future efforts should integrate digital health technologies and address structural barriers to optimize care efficiency worldwide. Research in Context: Evidence before this study: Prior to undertaking this analysis, we systematically reviewed the existing epidemiological literature on atrial fibrillation and atrial flutter (AF/AFL), with a particular emphasis on global and regional comparative studies. Our searches covered PubMed, Embase, Web of Science, the Cochrane Library, and the Global Burden of Disease (GBD) repository from January 1990 to December 2023, without language restrictions. Key terms included “atrial fibrillation,” “atrial flutter,” “global burden,” “epidemiology,” “trend,” and “GBD.” We included studies providing representative estimates of AF/AFL burden and excluded small-sample or non-age-standardized reports. Previous analyses indicated a rising global AF/AFL burden, largely due to population aging and improved detection. However, comprehensive assessments capturing temporal dynamics, risk drivers, and forecasting across major world regions—especially benchmarking China, Southeast Asia, and Europe against global patterns—remained limited. Most studies focused on isolated regions or short spans, lacking integrative multidimensional approaches such as age-period-cohort modeling, decomposition, or Bayesian forecasting. Added value of this study: This study provides a comprehensive and comparative assessment of the atrial fibrillation and atrial flutter (AF/AFL) burden across China, Southeast Asia, Europe, and globally from 1990 to 2021, utilizing the latest GBD 2021 data and advanced statistical methodologies, including Joinpoint regression, age-period-cohort modeling, Bayesian forecasting, decomposition analysis, and data envelopment frontier analysis. Our analysis reveals significant regional disparities against a backdrop of global stability: while the global age-standardized incidence rate (ASIR) remained stable (52·51 in 1990 vs. 52·12 in 2021), China experienced the most rapid increase worldwide (ASIR rising from 42·63 to 44·92), with a substantial number of new cases (916,180), accounting for 20·43% of the global total (4,484,926 cases). In contrast, Europe recorded a slight decline in ASIR. China also demonstrated the most pronounced increase in prevalence globally, while Europe’s age-standardized prevalence rate (ASPR) declined and the global rate remained largely unchanged. Notably, China achieved a significant reduction in mortality (age-standardized mortality rate [ASMR] declining from 4·93 to 4·33) despite rising incidence, sharply contrasting with Southeast Asia, where ASMR increased from 2·94 to 4·06 (estimated annual percentage change +1·07%)—trends potentially associated with structural challenges in Southeast Asia—while Europe maintained the highest ASMR globally (5·10 in 2021) despite interventions. We further identified key drivers:...