Animal magnetism, also known as mesmerism, is a theory invented by German doctor Franz Mesmer in the 18th century. It posits the existence of an invisible natural force (Lebensmagnetismus) possessed by all living things, including humans, animals, and vegetables.

Mesmerism, named after its chief theoretician and practitioner, Franz Anton Mesmer (1734-1815), also known as Animal Magnetism, was one of the most popular medical theories of the late eighteenth and early nineteenth centuries.

Mesmer termed the force animal gravity, later to become animal magnetism. In 1774 Mesmer began treating a young woman who had a long list of symptoms—fevers, vomiting, unbearable toothaches and earaches, delirium, and even occasional paralysis.