飞廉为一年或两年生（少数为多年生）草本植物，为菊科下的一个属。飞廉属约含有95个物种，在亚洲、欧洲和非洲都有分布，多为蜜源植物，也有少数可作为观赏植物。

在中国主要有以下三种飞廉：

• 垂头飞廉（Carduus nutans），也常常被直接称为飞廉；
• 丝毛飞廉（Carduus crispus）；
• 节毛飞廉（Carduus acanthoides）。

Carduus is a genus of flowering plants in the aster family, Asteraceae, and the tribe Cynareae, the thistles. It is one of two genera considered to be "true thistles", the other being Cirsium. Plants of the genus are known commonly as plumeless thistles. They are native to Eurasia and Africa, and several are known elsewhere as introduced species. This genus is noted for its disproportionately high number of noxious weeds compared to other flowering plant genera.