In medicine, hematuria, or haematuria, is the presence of red blood cells (erythrocytes) in the urine. It may be idiopathic and/or benign (Benignity), or it can be a sign (sign (medicine)) that there is a kidney stone or a tumor in the urinary tract (kidneys, ureters, urinary bladder, prostate, and urethra), ranging from trivial to lethal. If white blood cells are found in addition to red blood cells, then it is a signal of urinary tract infection.

Occasionally "hemoglobinuria" is used synonymously, although more precisely it refers only to hemoglobin in the urine.