Petasites hybridus, also known as the butterbur, is a herbaceous perennial flowering plant in the family Asteraceae that is native to Europe and northern Asia.

[2] In the British Isles, female plants are rarely found outside central and northern England and the species may be naturalized as clonal populations outside this area,[6]: 810  propagating via rhizome fragments.

[3] Although some preliminary studies indicate that butterbur may reduce the frequency of migraine headaches in adults and children, clinical neurology associations do not recommend it because of concerns of possible liver toxicity.

[3][4] Although there have been studies of butterbur root or leaf extracts as possible therapies for symptoms of hay fever (allergic rhinitis), the results were insufficient to determine effectiveness and safety.

[4] The adverse effects of butterbur reported in clinical trials include mainly gastrointestinal problems, such as nausea, flatulence, and belching.