A3 is a motorway in Portugal, connecting Valença and Porto via Braga. A3 is operated by Brisa - Auto-estradas de Portugal. It has a total length of 112km and coincides with the European itinerary number 1.

This motorway leaves the urban IC23 circular motorway around Porto and Gaia. This motorway passes through Maia, Braga and to the border town Valença. It is an important route for travellers who desire to enter Spain and the Spanish state called Galicia. The motorway is a toll road, and most of the route north is climbing steadily until reaching Spain. The motorway is linked by a bridge on the frontier and another motorway to link with Vigo and Pontevedra which is in Galicia. It is under the care of Brisa S.A