Cuiabá (kōyəbäˈ) [key], city (1996 pop. 443,101), capital of Mato Grosso state, SW Brazil, at the head of navigation on the Cuiabá River. Founded in the gold rush of the early 18th cent., it has been the state capital since 1818. The city is a trading center for an extensive cattle-raising and agricultural area. Economic development has been hampered by Cuiabá's isolation and by the shortage of labor. Riverboats remain an important means of communication.