The primary role of the hypothalamus in regulating body temperature is to maintain homeostasis. The hypothalamus, a small region located in the brain, acts as the body's thermostat. It receives input from various temperature receptors and responds by triggering mechanisms such as sweating or shivering to regulate body heat. By making adjustments to blood flow and metabolic rate, the hypothalamus ensures that the body maintains a stable internal temperature, which is vital for proper physiological function.