Diabetic kidney disease and diabetic nephropathy are the leading cause of end-stage kidney disease in the United States and most developed countries. Diabetes accounts for 30% to 50% of the incident cases of end-stage kidney disease in the United States. Although this represents a significant public health concern, it is important to note that only 30% to 40% of patients with diabetes develop diabetic nephropathy. Specific treatment of patients with diabetic nephropathy can be divided into 4 major arenas: cardiovascular risk reduction, glycemic control, blood pressure control, and inhibition of the renin-angiotensin system (RAS). Recommendations for therapy include targeting a hemoglobin A1c concentration < 7% and blood pressure < 140/90mmHg with therapy anchored around the use of a RAS-blocking agent. The single best evidence-based therapy for diabetic nephropathy is therapy with a RAS-blocking medication. This Core Curriculum outlines and discusses in detail the epidemiology, pathophysiology, diagnosis, and management of diabetic nephropathy.