Teresina (tārāzēˈnä) [key], city (1991 pop. 599,272), capital of Piauí state, NE Brazil, on the Parnaíba River. It is the main commercial and agricultural distribution center in the Parnaíba valley; cattle, hides and skins, rice, wax, beans, and cassava are shipped through the city. Its industries produce textiles, sugar, soap, and lumber. Teresina was a planned city formally established in 1852 and named for Brazilian Empress Teresa Cristina Maria.