唾液，亦称口涎、口水，是动物口腔内唾液腺分泌的无色且稀薄的液体，其在食物的消化过程中起到十分关键的作用。唾液主要由腮腺、颌下腺和舌下腺这三条唾液腺共同分泌出来；唾液的分泌受到大脑皮层的控制，也会受到饮食、环境、年龄以及情绪或唾液腺病变等影响。人每日分泌1,000-1,500毫升的唾液为正常现象。婴儿分泌的唾液比成人多。

一些动物的唾液除了参与消化之外还有其他的作用。例如燕子会使用唾液来帮助筑巢，其中雨燕或金丝燕的巢即为燕窝。

Saliva is a watery substance located in the mouths of humans and animals, secreted by the salivary glands. Human saliva is 99.5% water, while the other 0.5% consists of electrolytes, mucus, glycoproteins, enzymes, and antimicrobial agents such as secretory IgA and lysozyme. The enzymes found in saliva are essential in beginning the process of digestion of dietary starches and fats. These enzymes also play a role in breaking down food particles entrapped within dental crevices, protecting teeth from bacterial decay. Furthermore, saliva serves a lubricative function, wetting food and permitting the initiation of swallowing, and protecting the mucosal surfaces of the oral cavity from desiccation.