喷嚏，又称喷嚏反射，是一种人和动物的生理反射行为。

反射的感受器在鼻黏膜，由三叉神经传导到脑部。打喷嚏前，鼻子变得发酸、发痒。过程一般为急促吸气，张嘴，然后高速（可达每小时50公里）通过鼻腔和口腔同时排气，产生响亮的“阿─嚏”声音（粤语中以「乞嗤」形声表示）。打喷嚏时，唾液会形成1000-40000粒飞沫随空气高速喷出，速度达每小时177公里（即每秒约49.2米），所以是很多传染病的传染媒介。一般打喷嚏的同时还会闭眼，可能是为了避免飞沫污染。直径大于100微米的飞沫很快落地，小粒飞沫水分部分蒸发后，形成气溶胶，可以悬浮几个小时或更长。

A sneeze, or sternutation, is a semi-autonomous, convulsive expulsion of air from the lungs through the nose and mouth, usually caused by foreign particles irritating the nasal mucosa. A sneeze expels air forcibly from the mouth and nose in an explosive, spasmodic involuntary action resulting chiefly from irritation of the nasal mucous membrane. Sneezing is possibly linked to sudden exposure to bright light, sudden change (fall) in temperature, breeze of cold air, a particularly full stomach, or viral infection, and can lead to the spread of disease.