Prenanthes is a genus of plant in the family Asteraceae, often referred to as rattlesnake root.

Molecular analysis in 2009 revealed that the genus as traditionally envisioned was polyphyletic, meaning that it is a conglomeration of species not closely related to one another. The genus formerly included species now placed in Aetheorhiza, Askellia, Brickellia, Chondrilla, Crepidiastrum, Crepis, Emilia, Erythroseris, Faberia, Hololeion, Hypochaeris, Ixeris, Lactuca, Lapsanastrum, Launaea, Lygodesmia, Nabalus, Notoseris, Paraprenanthes, Parasenecio, Picrosia, Sonchella, Sonchus, Soroseris, Stephanomeria, Trixis, and Youngia.

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