In medicine, hematuria (or "haematuria") is the presence of red blood cells (erythrocytes) in the urine. It is a sign that there is a kidney stone or a tumor in the ureter, urinary bladder, prostate, or urethra. kidneys and the urinary tract, 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.