A sertão (, plural sertões) is the "hinterland" or "backcountry". In Brazil, it refers to one of the four sub-regions of the Northeast Region of Brazil (similar to the specific association of "outback" with Australia in English). Its borders are not precise and do not correspond to any modern Brazilian states. Like the South of the United States, it is a region that is well-known in Brazilian culture, with a rich history and much folklore.

Originally the term referred to the vast hinterlands of Asia and South America that Portuguese explorers encountered. In Brazil, it referred to backlands away from the Atlantic coastal regions where the Portuguese first settled in South America in the early sixteenth century. A Brazilian historian once referred to colonial life in Brazil as a "civilization of crabs", as most settlers clung to the shoreline, with few trying to make inroads into the sertão. In modern terms, "sertão" refers to a semi-arid region in northeastern Brazil, comprising parts of the states of Alagoas, Bahia, Pernambuco, Paraíba, Rio Grande do Norte, Ceará, Maranhão, Piauí, and Minas Gerais.

Geographically, the sertão consists mainly of low uplands that form part of the Brazilian Highlands. Most parts of the sertão are between 200 meters}} and and on the northern coast at Fortaleza, it is confined to a short rainy season. This season extends from January to April in the west, but in the eastern sertão it generally occurs from March to June. However, rainfall is extremely erratic and in some years the rains are minimal, leading to catastrophic drought, while in others rains are extremely heavy and floods occur. This variability has caused extreme famines among subsistence farmers in the region, exacerbated by the extreme imbalance of land ownership throughout the sertão.{{explain The worst of these famines, between 1877 and 1879, was said to have killed over half the region's population.

In its natural state, the sertão was covered by a distinctive scrubby caatinga vegetation, consisting generally of low thorny bushes adapted to the extreme climate. Several species of tree in the caatinga, such as the cashew, have become valuable horticultural plants. Most of the sertão vegetation is now substantially degraded as a result of centuries of cattle ranching or clearing for cotton farming.

Parts of the sertão are recognized as a biodiversity hot-spot because of its unique flora.

File:Grande Sertao Veredas 4.jpg|Sertão in the Grande Sertão Veredas National Park File:Rainbow at Brazilian Sertão (desert).JPG|Rainbow at Brazilian Sertão (desert). Cícero Dantas, Bahia, Brazil. File:2003SertaoNordestino.jpg|The Sertão (desert) of Brazil