To report the global, regional, and national burden of breast cancer (BC) and its attributable risk factors between 1990 and 2021, by age, sex, and sociodemographic index.

Using data from the Global Burden of Disease Study 2021, we analyzed BC prevalence, deaths, disability‐adjusted life years (DALYs), and attributable risk factors across 204 countries and territories from 1990 to 2021. Age‐standardized prevalence, deaths, and DALYs rates were estimated, and temporal trends were assessed using the estimated annual percentage change. Geographical and sociodemographic inequalities were further evaluated using decomposition analysis, concentration curves, and sociodemographic index (SDI)‐based modeling. Attributable risk factors for deaths and DALYs were quantified using the comparative risk assessment framework.

Globally, BC presents a starkly diverging landscape. While the age‐standardized prevalence has climbed to 239 per 100,000 (a 9.3% increase since 1990), the death and DALYs rates have actually declined by 13.7% and 9.8%, respectively. This global trend, however, masks a critical geographical shift. High‐income regions maintain the highest prevalence, yet the most rapid increases in burden are now concentrated in resource‐limited areas such as North Africa and the Middle East. The “triple threat” in low‐SDI regions defines this transition. Decomposition analysis revealed that while population growth and aging lead to absolute mortality everywhere, high‐SDI regions successfully offset this pressure through favorable epidemiological changes and advancements in screening and treatment. In contrast, low‐SDI regions face a deteriorating epidemiological profile that actively contributes to rising deaths. Our inequality analysis further underscores this systemic shift; concentration curves confirm that BC mortality is becoming disproportionately concentrated in lower‐SDI countries over time. Additionally, the disease follows a nonlinear, inverted U‐shaped relationship with socioeconomic development, peaking at an SDI of 0.75. Finally, we identified a distinct sex‐based etiological divide: while female risk patterns are multifaceted, male BC is almost singularly driven by metabolic dysregulation, with high body mass index emerging as the leading global driver of the disease.

Despite progress in reducing the BC burden, it remains a global public health challenge. The prevalence is high in developed countries, while the burden is rapidly increasing in low‐ and middle‐income countries.