Nephrology (from Greek νεφρός – nephros, "kidney", combined with the suffix -logy, "the study of") is a branch of internal medicine and pediatrics dealing with the study of the function and diseases of the kidney.

Nephrology concerns the diagnosis and treatment of kidney diseases, including electrolyte disturbances and hypertension, and the care of those requiring renal replacement therapy, including dialysis and renal transplant patients. Many diseases affecting the kidney are systemic disorders not limited to the organ itself, and may require special treatment. Examples include acquired conditions such as systemic vasculitides (e.g. ANCA vasculitis) and autoimmune diseases (e.g., lupus), as well as congenital or genetic conditions such as polycystic kidney disease.

Patients are referred to nephrology specialists for various reasons, such as acute renal failure, chronic kidney disease, hematuria, proteinuria, kidney stones, hypertension, and disorders of acid/base or electrolytes.

A nephrologist is a physician (MD, MBBS or DO) who has been trained in the diagnosis and management of kidney disease, by regulating blood pressure, regulating electrolytes, balancing fluids in the body, and administering dialysis. Nephrologists treat many different kidney disorders including acid-base disorders, electrolyte disorders, nephrolithiasis (kidney stones), hypertension (high blood pressure), acute kidney disease and end-stage renal disease. Nephrology is a subspecialty of internal medicine. In the United States, after medical school nephrologists complete a three year residency in internal medicine followed by a two year (or longer) fellowship in nephrology.