Stevia is a composite herb native to South America (Genus Stevia, especially S. rebaudiana, native to Paraguay) whose leaves are the source of a noncaloric sweetener.
Stevia is perhaps unique among food ingredients because it's most valued for what it doesn't do. It doesn't add calories. Unlike other sugar substitutes, stevia is derived from a plant.
The stevia plant is part of the Asteraceae family, related to the daisy and ragweed. Several stevia species called "candyleaf" are native to New Mexico, Arizona and Texas.
Prized species such as Stevia rebaudiana (Bertoni), grows in Paraguay and Brazil, where people have used leaves from the stevia bush to sweeten food for hundreds of years. In traditional medicine in these regions, stevia also served as a treatment for burns, colic, stomach problems and sometimes as a contraceptive.