The chile pepper species (or the genus Capsicum to which all the chile pepper species belong) is one of the many groups of plants among the nightshade family, the Solanaceae. Potatoes, tomatoes, eggplant also belong to this family, which includes many economically important species. The nightshades are also interesting because they produce alkaloid compounds, which are important medicinal resources, but also toxic substances.

The genus Capsicum is definitely American in origin; its centers of diversity, where the largest number of wild species can be found, are in the Brazilian Atlantic forest and in the Andes.

Two of the domesticated species of chilli can still be found mainly in the Andes and other parts of South America, C. pubescens (commonly known as rocoto) and C. baccatum (often called ají).

Capsicum annuum, frutescens and chinense – which form a species complex to botanists, meaning they are not strictly separated species – have their origin as cultivated species further north, in Central America and the Caribbean. C. annuum was particularly widely cultivated (and thus expanded into more varieties) in Mexico; C. frutescens may have had its main development in Central America; C. chinense is predominantly a Caribbean species.

From there, with the Columbian exchange (the spread of European species to the Americas and especially American species to Europe), the chile peppers spread globally. C. annuum, in particular, reached all around the world; C. frutescens has also seen some spread, but started out with few varieties and has remained so little diverse; C. chinense spread a bit farther but does not grow as easily as the others outside of tropical areas.