Cardiac surgery-associated acute kidney injury (CSA-AKI) represents a significant complication with immediate and long-term consequences. This chapter discusses the multifaceted nature of AKI pathophysiology during cardiopulmonary bypass (CPB), emphasizing hemodynamic instability, inflammatory responses, oxidative stress, and microembolization as principal contributory factors. The chapter details strategies for renal protection, focusing on optimizing perfusion, managing temperature, reducing inflammation, and using filtration techniques such as ultrafiltration. The text outlines the implications of AKI, including increased mortality rates, extended hospitalizations, and escalated healthcare costs. It also examines diagnostic classifications for AKI, risk stratification models, and emerging biomarkers for earlier detection and better prognosis. Moreover, the chapter reviews perioperative management guidelines aimed at minimizing renal injury, highlighting the importance of a comprehensive approach to enhance patient outcomes in cardiac surgery.