BACKGROUND: Despite the clinical importance of sepsis-associated acute kidney injury (SA-AKI), little is known about its epidemiology. We aimed to investigate the incidence and outcomes of SA-AKI, as well as the risk factors for mortality among patients with severe SA-AKI in critically ill patients. METHODS: This secondary multicenter, observational, prospective cohort analysis of sepsis in South Korea evaluated patients aged ≥ 19 years admitted to intensive care units with a diagnosis of sepsis. The primary outcome was the incidence of SA-AKI, defined using the new consensus definition of the Acute Disease Quality Initiative 28 Workgroup. Secondary outcomes were in-hospital mortality and risk factors for in-hospital mortality. RESULTS: Between September 2019 and December 2022, 5100 patients were admitted to intensive care units with a diagnosis of sepsis, and 3177 (62.3%) developed SA-AKI. A total of 613 (19.3%), 721 (22.7%), and 1843 (58.0%) patients had stage 1, 2, and 3 SA-AKI, respectively. Severe SA-AKI (stages 2 and 3 combined) was associated with an increased risk of in-hospital mortality. Adherence to the fluid resuscitation component of the one-hour sepsis bundle was associated with a decreased risk of in-hospital mortality in severe SA-AKI (adjusted odds ratio, 0.62; 95% confidence interval, 0.48-0.79; P < 0.001). CONCLUSIONS: Of the patients admitted to the intensive care unit for sepsis, 62.3% developed SA-AKI. Severe SA-AKI was associated with an increased risk of mortality. Adherence to the fluid resuscitation component of the one-hour sepsis bundle can potentially improve outcomes in these patients.