oxeye, name for several plants, e.g., the oxeye daisy and black-eyed Susan, but particularly for two genera: Heliopsis, native to North America, and Buphthalmum, native to Europe and W Asia but cultivated elsewhere. Both are perennials of the family Asteraceae (aster family) and are grown as ornamentals for their showy yellow heads. Oxeyes are classified in the division Magnoliophyta, class Magnoliopsida, order Asterales, family Asteraceae.