胭脂素，又称胭脂树橙、红木素。是一种在胭脂树红中发现的脱辅基类胡萝卜素，胭脂树红中包含5%的色素和70-80%的胭脂素。

胭脂素可溶于油脂，难溶于水。

Bixin is an apocarotenoid found in annatto, a natural food coloring obtained from the seeds of the achiote tree (Bixa orellana). Annatto seeds contain about 5% pigments, which consist of 70-80% bixin.

Bixin is chemically unstable when isolated and converts via isomerization into trans-bixin (β-bixin), the double-bond isomer.