This study investigates whether Body Roundness Index (BRI), an anthropometric measure derived from waist circumference and height, can predict mortality in adult intensive care unit (ICU) patients. BRI captures central adiposity and body fat distribution more accurately than Body Mass Index (BMI). In this prospective multicenter cohort study, BRI will be measured at ICU admission and its association with ICU mortality, 28-day mortality, hospital mortality, mechanical ventilation duration, ICU length of stay, and acute kidney injury will be evaluated. The predictive performance of BRI will also be compared with BMI.