Polydipsia is excessive thirst or excess drinking. The word derives from the Greek πολυδίψιος (poludípsios) "very thirsty", which is derived from πολύς (polús, "much, many") + δίψα (dípsa, "thirst"). Polydipsia is a nonspecific symptom in various medical disorders. It also occurs as an abnormal behaviour in some non-human animals, such as in birds.
In Chinese medicine, excessive thirst denotes heat; thirst without the desire to drink is a sign of dampness or deficient yin.
Polydipsia is a symptom of diabetes.