Abstract Introduction Fluid accumulation is associated with adverse outcomes in critically ill patients admitted to the intensive care unit (ICU). Fluid administration in the ICU may be a clinically relevant source of fluid accumulation in ICU patients. However, the extent is unknown, and no standard definition exists. We aim to provide epidemiological data on fluid accumulation, risk factors, use of fluid removal strategies, patient outcomes and describe current fluid administration practices in the ICU. Methods We will conduct an international 14‐day inception cohort study including a minimum of 1000 acutely admitted adult ICU patients. Data will be collected from medical records and laboratory reports at baseline and daily from ICU admission to discharge with a maximum of 28 days. Follow‐up will be performed on day 90 after inclusion. The primary outcome is the number of patients with fluid accumulation. Secondary outcomes include the number of days with fluid accumulation, use of active fluid removal, days alive without life support at day 28, days alive and out of hospital day 90, and all‐cause mortality at day 90. Furthermore, we will assess risk factors for fluid accumulation and its association with 90‐day mortality and report on the types of fluid administration. Conclusion This international inception cohort study will provide contemporary epidemiological data on fluid administration and fluid accumulation in adult ICU patients.