Bile or gall is an alkaline, green-yellow fluid. It is secreted from the liver of most vertebrate animals, and is often stored in the gall bladder. Bile helps digest fat.

The components of bile are, in descending order of composition, are:

The name gall comes from the Greek word cholè meaning green or yellow. These colours come from the bile pigments. One of them is green and the other is yellow. When they are mixed together, they make feces brown. The term cholesterol and the illness cholera were named after gall.

Bile is also stored in bile ducts. Often after liver transplants, bile comes out of the body.

Bile increases fats' total surface area to volume ratio so their digestion is easier and faster. Hence, more fats and fat-soluble vitamins like vitamins A, D, E and K can be absorbed. This keeps fat out of feces so they are brown instead of white, grey or greasy.