Eurybia is a genus of plants in the family Asteraceae that were previously included in the genus Aster. Most species are native to North America, although one is also present in northern Eurasia. There are 23 species in the genus, including 1 natural hybrid. The name was first applied by Alexandre de Cassini in 1820. The name is derived from Ancient Greek εὐρύς (eurús), meaning "wide", and βαιός (baiós), meaning "few", perhaps in reference to the small number of relatively wide ray florets.

Aster is a genus of perennial flowering plants in the family Asteraceae. Its circumscription has been narrowed, and it now encompasses around 170 species, all but one of which are restricted to Eurasia; many species formerly in Aster are now in other genera of the tribe Astereae. Aster amellus is the type species of the genus and the family Asteraceae.