Simsia is a genus of flowering plants in the sunflower tribe within the daisy family. It includes annuals, herbaceous perennials, and shrubs. They range from the western United States south through Central and South America to Argentina, with the center of diversity occurring in Mexico. The genus is named for British physician and botanist John Sims (1749–1831). Although some species are relatively rare, others have become common weeds that line the roadsides and fields of Mexico, often forming dense stands mixed with Tithonia and other Asteraceae. Some species are known by the common name bushsunflower.