Portugal–Spain border

The Tagus ( ; ; ) is the longest river in the Iberian Peninsula. The river rises in the Montes Universales between Cuenca and Teruel, in mid-eastern Spain, flows , generally westward, and empties into the Atlantic Ocean at Lisbon.

The Douro (, , , ; ; ) is the largest river of the Iberian Peninsula by discharge. It rises near Duruelo de la Sierra in the Spanish province of Soria, meanders briefly south, then flows generally west through the northern part of the Meseta Central in Castile and León into northern Portugal. Its largest tributary (carrying more water than the Douro at their confluence) is the right-bank Esla. The Douro flows into the Atlantic Ocean at Porto, the second largest city of Portugal.

Olivenza () or Olivença () is a town in southwestern Spain, close to the Portugal–Spain border. It is a municipality belonging to the province of Badajoz, and to the wider autonomous community of Extremadura.

river in Portugal and Spain

international border in Europe

upright|200px|thumb|Ardila River. Moura, Portugal The Ardila (; ) is a river of Spain and Portugal and a tributary of the Guadiana. Its length is . A portion of the river forms the Portugal–Spain border.

dam in the river Douro, Mogadouro, Portugal

dam in the river Douro, Spain

treaty between Spain and the Kingdom of Portugal (1864)

river in Portugal

protected area in Portugal

river in Spain and Portugal

1926 agreement between Portugal and Spain