Leather is made from animal skin, rawhide, as some call it. Animal skin, yours included, is made of a polymer called collagen. So is your hair and your fingernails. Collagen belongs to the family of polymers called proteins .
Proteins are one of many naturally occuring polymers .
They are also are a type of polyamide, and are in fact very similar to nylon . Rawhide is made into leather by a process called tanning, in which the collagen in the rawhide is crosslinked to make it stronger, more durable, and to keep it from rotting.