What is the human body's largest organ?

The human body’s largest organ is the skin. It forms the body’s outer covering and belongs to the integumentary system, protecting tissues from injury, pathogens, dehydration, and temperature changes.

Skin has three commonly discussed regions: the epidermis, dermis, and underlying hypodermis. The epidermis is the outer barrier; the dermis contains blood vessels, nerves, hair follicles, and glands; and the hypodermis contains much of the body’s subcutaneous fat and connective tissue. Together, these structures help regulate temperature, provide sensation, support immune defence, and contribute to vitamin D production.

People sometimes hear that the small intestine has a larger “surface area.” That comparison usually refers to the intestine’s highly folded internal lining, not an external organ covering. In standard anatomy quizzes, skin is the accepted answer for the largest organ, especially when considering its mass and external coverage. Its area varies with body size but is commonly about 1.5–2 square metres in adults.