Sumac or sumach is any of about 35 species of flowering plants in the genus Rhus and related genera in the cashew family (Anacardiaceae). Sumacs grow in subtropical and temperate regions throughout every continent except Antarctica and South America. Sumac is used as a spice, as a dye, and in medicine.

The Anacardiaceae, commonly known as the cashew family or sumac family, are a family of flowering plants, including about 83 genera with about 860 known species. Members of the Anacardiaceae bear fruits that are drupes and in some cases produce urushiol, an irritant. The Anacardiaceae include numerous genera, several of which are economically important, notably cashew, mango, Chinese lacquer tree, yellow mombin, Peruvian pepper, poison ivy, poison oak, sumac, smoke tree, marula and cuachalalate. The genus Pistacia is now included, but was previously placed in its own family, the Pistaciaceae.