蓼蓝（学名：Polygonum tinctorium），亦略称为蓝或靛青，为蓼科一年生的草本植物。主要用作染色及药用。

蓼蓝植株高约50公分到80公分，叶互生，卵形或椭圆形，叶下表面沿叶脉常有毛茸分布；鞘状托叶 (ocrea) 管状、膜质，长1-1.5厘米。

花为紫红色。原产地从中南半岛到中国。 蓼蓝亦有在欧洲生长，是当地的主要蓝染植物)。蓼蓝的外貌跟犬蓼有点类似。

Persicaria tinctoria is a species of flowering plant in the buckwheat family. Common names include Chinese indigo and "Japanese indigo." It is native to Eastern Europe and Asia.

The leaves were a source of indigo dye. It was already in use in the Western Zhou period (ca. 1045-771 B.C.), and was the most important blue dye in East Asia until the arrival of Indigofera from the south.