A processed cholesterol from Sheep's wool. It is essentially a fat that is excreted through the sheep's skin and gathers on the bottom of the wool hair follicles.
Crude lanolin constitutes approximately 5–25% of the weight of freshly shorn wool. The wool from one Merino sheep will produce about 250–300 ml of recoverable wool grease. Lanolin is extracted by washing the wool in hot water with a special wool scouring detergent to remove dirt, wool grease (crude lanolin), suint (sweat salts), and anything else stuck to the wool. The wool grease is continuously removed during this washing process by centrifugal separators, which concentrate the wool grease into a wax-like substance melting at approximately 38 °C
This is almost always vegetarian as producers don't want to kill the sheep that create the wool.