The largest organ in the human body is the one you can see most easily: the skin. The skin is considered an organ because it has some very specific functions — like maintaining body temperature and protecting the other organs from bacteria — that require some specialized tissues.
The skin of an average adult has a surface area of over 21 square feet and accounts for 6% to 10% of your body weight, edging out the liver, your body's second-largest organ, which accounts for approximately 2.5% of your body weight.