Background Sepsis surveillance using electronic health record (EHR)-based data may provide more accurate epidemiologic estimates than administrative data, but experience with this approach to estimate population-level sepsis burden is lacking. Methods This was a retrospective cohort study including all adults admitted to publicly funded hospitals in Hong Kong between 2009 and 2018. Sepsis was defined as clinical evidence of presumed infection (clinical cultures and treatment with antibiotics) and concurrent acute organ dysfunction (>= 2-point increase in baseline Sequential Organ Failure Assessment [SOFA] score). Trends in incidence, mortality, and case fatality risk (CFR) were modeled by exponential regression. Performance of the EHR-based definition was compared with 4 administrative definitions using 500 medical record reviews. Results Among 13 540 945 hospital episodes during the study period, 484 541 (3.6%) had sepsis by EHR-based criteria with 22.4% CFR. In 2018, age- and sex-adjusted standardized sepsis incidence was 756 per 100 000 (relative change: +2.8%/y [95% CI: 2.0%-3.7%] between 2009 and 2018) and standardized sepsis mortality was 156 per 100 000 (relative change: +1.9%/y; 95% CI: .9%-2.8%). Despite decreasing CFR (relative change: -0.5%/y; 95% CI: -1.0%, -.1%), sepsis accounted for an increasing proportion of all deaths (relative change: +3.9%/y; 95% CI: 2.9%-4.8%). Medical record reviews demonstrated that the EHR-based definition more accurately identified sepsis than administrative definitions (area under the curve [AUC]: .91 vs .52-.55; P < .001). Conclusions An objective EHR-based surveillance definition demonstrated an increase in population-level standardized sepsis incidence and mortality in Hong Kong between 2009 and 2018 and was much more accurate than administrative definitions. These findings demonstrate the feasibility and advantages of an EHR-based approach for widescale sepsis surveillance.