汗液，或汗，是由人等高等动物透过汗腺所分泌出的液体。汗的分泌受到植物性神经系统调节。

• 降温：在汗腺排出汗液的过程中，汗液的排出和蒸发帮助生物体表带走大量的热量，达到散热的目的；
• 保护：湿润皮肤、软化角质，酸化并抑制细菌；
• 排泄：排出体内毒素及废物。

Perspiration, also known as sweating or diaphoresis, is the production of fluids secreted by the sweat glands in the skin of mammals.

Two types of sweat glands can be found in humans: eccrine glands and apocrine glands. The eccrine sweat glands are distributed over much of the body.