Cestona (officially Zestoa in Basque) is a town in the province of Gipuzkoa, within the autonomous community of the Basque Country in northern Spain. It lies in the Urola River valley in the northeastern part of the Iberian Peninsula, near the coast of the Bay of Biscay.
The town is known in Spain for its spa, the Balneario de Cestona, whose mineral waters have been used since the 18th century. The historic quarter preserves traditional Basque architecture, including the parish church and several manor houses.