Humorism, the humoral theory, or humoralism, was a system of medicine detailing a supposed makeup and workings of the human body originated in Persia (Iran) and adopted by Ancient Greek and Roman physicians and philosophers after contact with the Persians.

Humorism began to fall out of favor in the 1850s with the advent of germ theory, which was able to show that many diseases previously thought to be humoral were in fact caused by pathogens.