The liver is the largest internal organ in the human body. It sits mainly in the upper-right portion of the abdomen, beneath the diaphragm and partly behind the lower ribs. In adults, it commonly weighs about 1.4 to 1.8 kilograms, although size varies with body size and other factors.
The liver performs hundreds of important functions. It processes nutrients absorbed from the digestive tract, helps regulate blood chemistry, produces bile for fat digestion, stores glycogen, and helps break down medicines and toxins. It also makes many proteins involved in blood clotting and transports substances through the bloodstream.
People sometimes answer “skin” when asked for the largest organ overall. That is correct for the body’s largest organ, but the question asks specifically about an organ inside the body. The lungs are sometimes treated as a combined organ system, yet the liver is generally recognized as the largest single internal organ and the largest gland.