Eumerus is a genus of hoverflies (family Syrphidae), within the tribe Eumerini. They are small with a distinctive smooth round abdomen, powerful back legs and yellow hairs around the scutellum. Others have a dark scutellum and yellow antennae. They have a flat hairy face and a reentrant upper crossvein on the wings. Some species are pests of ornamental flowers. The genus contains 281 known species, making it one of the largest genera of flies.