The Douro line is a 99-mile railway line in northern Portugal that runs from Ermesinde to the eastern terminus at Pocinho. The line runs close to the Douro River for much of its route, offering scenic views of the river and valley. Passenger trains are operated by Comboios de Portugal (CP) and run between Porto São Bento and Pocinho, taking 3 hours and 20 minutes. Freight trains operated by Medway also run on the line.

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 is the right-bank Esla. The Douro flows into the Atlantic Ocean at Porto, the second largest city of Portugal.