土荆芥（学名：Dysphania ambrosioides），又名臭草、杀虫芥、鸭脚草。是苋科刺藜属的植物。

一年生或多年生草本，具有椭圆形腺体，芳香；茎有棱多分枝；披针形的叶子，有不整齐的齿，下面有黄色腺点；穗状花序，花两性或雌性，通常35朵簇生于苞腋；扁球形苞果。

Dysphania ambrosioides, formerly Chenopodium ambrosioides, known as wormseed, Jesuit's tea, Mexican-tea, payqu (paico), epazote, or herba sancti Mariæ, is an annual or short-lived perennial herb native to Central America, South America, and southern Mexico.