乳香（frankincense）是一种由橄榄科植物乳香木（学名：Boswellia thurifera 或Boswellia sacra）产出的含有挥发油的香味树脂。乳香的古法文为franc encens，表示「真/贵重」「香料」，形容它在古代欧洲多贵重。该说法现在还在许多欧洲语言中使用。乳香一词是因为阿拉伯文称之为「奶」（al-lubán）而来，理由是树脂从乳香木滴出时像乳液一样。乳香产于乳香木，采集方法是在树皮上割开伤口，流出乳状汁液，接触空气后变硬，成为黄色微红的半透明凝块。乳香主要产地是索马里、也门、阿曼的佐法尔和哈德拉毛地区，古代的集散中心是以示巴王国为中心的也门地区。

Frankincense, also called olibanum, is an aromatic resin used in incense and perfumes, obtained from trees of the genus Boswellia in the family Burseraceae, particularly Boswellia sacra (syn: B. bhaw-dajiana), B. carterii, B. frereana, B. serrata (B. thurifera, Indian frankincense), and B. papyrifera. The English word is derived from Old French "franc encens" (i.e., high quality incense).