A3 is a motorway in northern Portugal, connecting Valença and Porto via Braga to the Portugal–Spain border, on the Minho River at Tui, where it connects to the Autovía A-55 in Galicia (Spain).

It has a total length of 112 km and coincides with the European itinerary number 1.

This motorway passes through Maia, Braga and to the border town Valença.

The motorway is a toll road, and most of the route north is climbing steadily until reaching Spain.

It is under the care of Brisa S.A Sections of the road carry very little traffic.