麻风病（英语：Leprosy），又作麻疯病、痲疯病、癞病、疠风等。医学领域称为汉生病或韩森氏病（英语：Hansen's Disease），是由麻风杆菌与弥漫型痲疯分枝杆菌引起的一种慢性传染病，主要经由飞沫传染但传染性并不强。感染初期并不会出现症状，潜伏期可达5至20年。该疾病会在神经系统、呼吸道、皮肤与眼部出现肉芽肿。这会导致病患失去痛觉感知的能力，造成四肢因反复受伤而需部分截肢。也可能出现虚弱与视力变差的症状。

视不同的细菌数量，麻风病可分为两种主要的类型：少菌型（英语：paucibacillary）与多菌型（英语：multibacillary）。两个类型主要是由皮肤感觉迟钝甚至消失的白色斑块病变量量来分，少于五个病变称为少菌型，多于五个则是多菌型。确诊麻风病的方式有二：一是在皮肤切片下找到耐酸性染色阳性菌；二是以聚合酶连锁反应侦测细菌DNA的存在。麻风病的感染者多为经济状况不佳者，并多以飞沫传染的途径传播。此病传染性并不高。

Leprosy, also known as Hansen's disease (HD), is a long term infection caused by the bacteria Mycobacterium leprae and Mycobacterium lepromatosis. Initially, infections are without symptoms and typically remain this way from 5 to as long as 20 years. Symptoms that develop include granulomas of the nerves, respiratory tract, skin, and eyes. This may result in a lack of ability to feel pain and thus loss of parts of extremities due to repeated injuries or infection due to unnoticed wounds. Weakness and poor eyesight may also be present.