Nephrology  is a specialty of medicine and pediatric medicine that concerns with study of the kidneys, specifically normal kidney function and kidney disease, the preservation of kidney health, and the treatment of kidney disease, from diet and medication to renal replacement therapy (dialysis and kidney transplantation).

Nephrology also studies systemic conditions that affect the kidneys, such as diabetes and autoimmune disease; and systemic diseases that occur as a result of kidney disease, such as renal osteodystrophy and hypertension. A physician who has undertaken additional training and become certified in nephrology is called a nephrologist.

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. The word 'dialysis' is from the mid 19th century: via Latin from the Greek word 'dialusis'; from 'dialuein' (split, separate), from 'dia' (apart) and 'luein' (set free). In other words, dialysis replaces the primary (excretory) function of the kidney, which separates (and removes) excess toxins and water from the blood, placing them in the urine.

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 after a urinalysis, for various reasons, such as acute kidney injury, chronic kidney disease, hematuria, proteinuria, kidney stones, hypertension, and disorders of acid/base or electrolytes.