毒芹（学名：Cicuta virosa）为伞形科毒芹属的植物。

多年生高大草本，根状茎肥大垂直，早春时结果实，秋季时中空具横隔。二或三回羽状全裂的叶片，最终叶片为狭披针形或披针形，具有尖锯齿。复伞形花序，白色花。近球形的双悬果两侧压扁。

根状茎有香气，切口有淡黄色树脂状液体流出，遇到空气则变暗。

Cicuta virosa (cowbane or northern water hemlock) is a species of Cicuta, native to northern and central Europe, northern Asia and northwestern North America. It is a perennial herbaceous plant which grows up to 1–2 m tall. The stems are smooth, branching, swollen at the base, purple-striped, and hollow except for partitions at the junction of the leaves and stem. In cross section the stems have one flat side and the other sides are rounded. The leaves are alternate, tripinnate, only coarsely toothed, unlike the ferny, lacy leaves found in many other members of the family Apiaceae. The flowers are small, white and clustered in umbrella shaped inflorescences typical of the family. The many flowered umbellets have unequal pedicels that range from 5 to 11 cm long during fruiting. An oily, yellow liquid oozes from cuts to the stems and roots. This liquid has a rank smell resembling that of parsnips or carrots. The plant may be mistaken for parsnip due to its clusters of white tuberous roots.