哮喘（来源于希腊语 ἅσθμα, ásthma，“panting”）是一种常见的气道的慢性炎症性疾病，主要特征是多变和复发的症状、可逆性气流阻塞，和支气管痉挛。常见症状表现为喘息、咳嗽、胸腔紧迫胸闷和气短。

哮喘普遍认为是由基因和环境因素共同导致的。对哮喘的诊断通常基于症状的类型、随时间推移对治疗的反应，及呼吸量测定法。医学上对哮喘的分类依据是发病频率、一秒内用力呼吸量（FEV1），和呼气流量峰值。哮喘也可以被分为特应性（外来的）或非特应性（固有的）此处特应性指的是向类别1型超敏性反应发展的倾向。

Asthma is a common long term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include episodes of wheezing, coughing, chest tightness, and shortness of breath. These episodes may occur a few times a day or a few times per week. Depending on the person they may become worse at night or with exercise.