紫芳草（学名：Exacum affine）为龙胆科紫芳草属下的一个种。

Exacum affine (syn. Exacum socotranum, Exacum gracilipes) known commercially as the Persian Violet, is a species of plant in the family Gentianaceae. It is endemic to Socotra, part of Yemen. Its natural habitat is rocky areas. A small herbaceous biennial plant with dark green, ovate leaves. The small purple flowers have a yellow centre with fragrance.