The Tambre is a coastal river that crosses Galicia, in northwestern Spain.

Its basin covers 1,531 square kilometres (591 sq mi).

The river flows through the province of A Coruña; the municipalities along its course are Sobrado, Curtis, Vilasantar, Boimorto, Mesía, Frades, Arzúa, O Pino, Oroso, Ordes, Trazo, Tordoia, Santiago de Compostela, Val do Dubra, Ames, A Baña, Brion, Negreira, Outes, Mazaricos, Noia and Lousame.

Its mouth forms the Ría de Muros e Noia estuary.

In ancient times it was called Támaris, its name being related to that of the River Tamar in Cornwall.