Summary Background Epidemiological data for acute kidney injury are scarce, especially in low-income countries (LICs) and lower-middle-income countries (LMICs). We aimed to assess regional differences in acute kidney injury recognition, management, and outcomes. Methods In this multinational cross-sectional study, 322 physicians from 289 centres in 72 countries collected prospective data for paediatric and adult patients with confirmed acute kidney injury in hospital and non-hospital settings who met criteria for acute kidney injury. Signs and symptoms at presentation, comorbidities, risk factors for acute kidney injury, and process-of-care data were obtained at the start of acute kidney injury, and need for dialysis, renal recovery, and mortality recorded at 7 days, and at hospital discharge or death, whichever came earlier. We classified countries into high-income countries (HICs), upper-middle-income countries (UMICs), and combined LICs and LMICs (LLMICs) according to their 2014 gross national income per person. Findings Between Sept 29 and Dec 7, 2014, data were collected from 4018 patients. 2337 (58%) patients developed community-acquired acute kidney injury, with 889 (80%) of 1118 patients in LLMICs, 815 (51%) of 1594 in UMICs, and 663 (51%) of 1241 in HICs (for HICs vs UMICs p=0.33; p<0.0001 for all other comparisons). Hypotension (1615 40% patients) and dehydration (1536 38% patients) were the most common causes of acute kidney injury. Dehydration was the most frequent cause of acute kidney injury in LLMICs (526 46% of 1153 vs 518 32% of 1605 in UMICs vs 492 39% of 1260 in HICs) and hypotension in HICs (564 45% of 1260 vs 611 38%% of 1605 in UMICs vs 440 38% of 1153 LLMICs). Mortality at 7 days was 423 (11%) of 3855, and was higher in LLMICs (129 12% of 1076) than in HICs (125 10% of 1230) and UMICs (169 11% of 1549). Interpretation We identified common aetiological factors across all countries, which might be amenable to a standardised approach for early recognition and treatment of acute kidney injury. Study limitations include a small number of patients from outpatient settings and LICs, potentially under-representing the true burden of acute kidney injury in these areas. Additional strategies are needed to raise awareness of acute kidney injury in community health-care settings, especially in LICs. Funding International Society of Nephrology.