Sestao is a Spanish city in the province of Biscay, in the Autonomous Region of the Basque Country.

Sestao has 28 651 inhabitants (as of 1 January 2013). Sestao is located on the left bank of the Ría de Bilbao, is a suburb of the city of Bilbao. Sestao was by the Altos Hornos de Vizcaya, a major steel industrial site.