The organ that filters blood in the human body is the kidney. Humans typically have two kidneys, located on either side of the spine, and they play a critical role in maintaining homeostasis. Kidneys filter waste products and excess substances from the blood, which are then excreted as urine. They also regulate electrolyte balance, blood pressure, and red blood cell production through hormone secretion. This essential organ is vital for overall health and proper bodily function.