体液学说（英语：Humorism，Humoralism或Humorae theory），起源于古希腊的医学理论，认为人体是由四种体液构成－血液、黏液、黄胆汁和黑胆汁，这四种体液对应到四种元素、四种气质，四种体液在人体内失去平衡就会造成疾病，又称为四体液学说、四体液说。

这个学说在希腊化时代广泛传至地中海区，受希波克拉底著作影响，古罗马医学、波斯医学、伊斯兰医学、**都以古希腊的体液学说为理论基础。印度医学受古希腊医学影响，也采用四体液学说。**受印度医学影响，间接继承了体液学说。汉医学也因受印度医学影响，而采取了部份体液学说的看法

Humorism, or humoralism, was a system of medicine detailing the makeup and workings of the human body, adopted by the Indian Ayurveda system of medicine, and Ancient Greek and Roman physicians and philosophers, positing that an excess or deficiency of any of four distinct bodily fluids in a person—known as humors or humours—directly influences their temperament and health. The humoralist system of medicine was highly individualistic, for each individual patient was said to have their own unique humoral composition. Moreover, it resembled a holistic approach to medicine as the link between mental and physical processes were emphasized by this framework. From Hippocrates onward, the humoral theory was adopted by Greek, Roman and Islamic physicians, and became the most commonly held view of the human body among European physicians until the advent of modern medical research in the nineteenth century. The concept has not been used in medicine since then.