BACKGROUND: Acute Kidney Injury (AKI) is a frequent complication of severe SARS-CoV-2 infection. Multiple mechanisms are involved in COVID-19-associated AKI, from direct viral infection and secondary inflammation to complement activation and microthrombosis. However, data are limited in critically-ill patients. In this study, we sought to describe the prevalence, risk factors and prognostic impact of AKI in this setting. METHODS: Retrospective monocenter study including adult patients with laboratory confirmed SARS-CoV-2 infection admitted to the ICU of our university Hospital. AKI was defined according to both urinary output and creatinine KDIGO criteria. RESULTS: Overall, 100 COVID-19 patients were admitted. AKI occurred in 81 patients (81%), including 44, 10 and 27 patients with AKI stage 1, 2 and 3 respectively. The severity of AKI was associated with mortality at day 28 (p = 0.013). Before adjustment, the third fraction of complement (C3), interleukin-6 (IL-6) and ferritin levels were higher in AKI patients. After adjustment for confounders, both severity (modified SOFA score per point) and AKI were associated with outcome. When forced in the final model, C3 (OR per log 0.25; 95% CI 0.01-4.66), IL-6 (OR per log 0.83; 95% CI 0.51-1.34), or ferritin (OR per log 1.63; 95% CI 0.84-3.32) were not associated with AKI and did not change the model. CONCLUSION: In conclusion, we did not find any association between complement activation or inflammatory markers and AKI. Proportion of patients with AKI during severe SARS-CoV-2 infection is higher than previously reported and associated with outcome.