Abstract Background It is unclear whether individuals with Down syndrome (DS) are at increased risk of kidney disease. This study aims to examine the risk of acute kidney injury (AKI) and chronic kidney disease (CKD) in individuals with DS compared to the general population. Methods Using the Danish Cytogenetic Central Registry, we identified a population-based cohort of individuals with genetically confirmed DS in Denmark between 1961 and 2021. For each individual with DS, we sampled 10 age-and-sex-matched individuals without DS from the general Danish population. We used laboratory data on plasma creatinine from the 1990s until 2024 to assess AKI and CKD and computed the cumulative incidence (risk) of AKI and CKD by age. Furthermore, we estimated the risk of AKI and CKD in individuals without congenital heart disease (CHD). Results We identified 2,815 individuals with DS and available laboratory data on plasma creatinine measurements. Comparing individuals with DS to the matched cohort, the risk of AKI was 28.9% vs. 1.4% at age 20, 32.8% vs. 5.3% at age 40, and 48.6% vs. 23.8% at age 70. The risk of CKD was 1.2% vs. 0.1% at age 20, 3.9% vs. 0.4% at age 40, and 23.2% vs. 13.8% at age 70. For individuals without CHD, the risk of AKI and CKD remained considerably higher for individuals with DS than for matched individuals. Conclusions Individuals with DS were at increased risk of both AKI and CKD compared to the general population. Kidney disease should be considered during clinical follow-up of DS.