白三烯（Leukotriene, LTs）是一类含三个共轭双键的20碳直链羟基酸的总称,是与过敏性反应有关的生物活性物质，其他与过敏性反应有关的生物活性物质包括组胺、缓激肽、血小板活化因子等。白三烯由于最早是在白细胞中发现故而得名。它们在体内的主要作用是引起气管平滑肌的收缩，同时也增加微血管通透性。白三烯的过多释放是引起哮喘和过敏性鼻炎的主要原因之一。白三烯拮抗剂(Leukotriene antagonist)可通过抑制白三烯的产生和活动达到治疗哮喘和过敏性鼻炎的效果。

Leukotrienes are a family of eicosanoid inflammatory mediators produced in leukocytes by the oxidation of the essential fatty acids arachidonic acid (AA) and eicosapentanoic acid (EPA) by the enzyme arachidonate 5-lipoxygenase. As their name implies, leukotrienes were first discovered in leukocytes, but have since been found in other immune cells.