Teresina is the capital and most populous municipality in the Brazilian state of Piauí. Being located in north-central Piauí 366 km from the coast, it is the only capital in the Brazilian Northeast that is not located on the shores of the Atlantic Ocean. With 871,126 inhabitants, Teresina is the 21st largest city in Brazil, and the 15th largest state capital in the country. Together with Timon in the nearby state of Maranhão, it forms a conurbation with a population of about 978,734 inhabitants; the entire metropolitan region of Teresina has over 1,226,509 inhabitants. The only natural barrier that separates Teresina from Timon is the Parnaíba river, one of the largest in the Northeast.

Teresina–Senador Petrônio Portella Airport is the airport serving Teresina, Brazil. Since December 22, 1999 it is named after Petrônio Portella Nunes (1925-1980) a former Mayor of Teresina, Governor of Piauí, Senator and Minister of Justice.