支气管扩张药（英语：bronchodilator）是一种扩张支气管与细支气管的物质，降低呼吸系统阻力并增加通往肺部的气流量。支气管扩张药可以是内源性的（机体内自然产生的），也可以通过给药的方式服用以治疗呼吸困难。这些药物在阻塞性肺疾患中最有效，后者最常见的症状是哮喘与慢性阻塞性肺病。尽管仍存有一些争议，这些药物可能对细支气管炎是有效的。在治疗限制性肺疾病时常会开这些药，但效果未经证实。

抗高血压药 · 利尿剂 · 血管舒张剂 · β受体阻断剂 · 钙信道阻断剂 · 肾素-血管紧张素系统（ACE抑制剂、血管紧张素Ⅱ受体拮抗剂、肾素抑制剂）

A bronchodilator is a substance that dilates the bronchi and bronchioles, decreasing resistance in the respiratory airway and increasing airflow to the lungs. Bronchodilators may be endogenous (originating naturally within the body), or they may be medications administered for the treatment of breathing difficulties. They are most useful in obstructive lung diseases, of which asthma and chronic obstructive pulmonary disease are the most common conditions. Although this remains somewhat controversial, they might be useful in bronchiolitis and Bronchiectasis.They are often prescribed but of unproven significance in restrictive lung diseases.