São Martinho do Porto is a freguesia (civil parish) in Alcobaça Municipality and in the Oeste region of Portugal.

The parish has one of the most beautiful beaches in the country, a bay, shaped like a scallop, with calm waters and fine white sand. São Martinho do Porto was even considered the best beach to go with the family in the guide of 2015 beaches of eDreams. According to the online booking site for travel and hotels, the "natural bay of clear and calm water and surrounded by diverse shops and restaurants offers the ideal conditions for a relaxed family day". In addition, the company, based in Barcelona, says that "it is perfect for the baths of children, while adults relax in the sand or have a drink on a terrace overlooking the sea".

Although the commercial importance of the port has diminished, its tourist activity and the beach life give it a special dynamic, especially during the summer season.

The bay is only connected to the sea by an opening of a few meters. Hence the waters are quiet, great for children and better still for competitions of sailing, windsurf or kayak. The road by the sea, where parking is difficult, has numerous cafes, restaurants and terraces. A narrow pedestrian tunnel gives direct access to the ocean from the dock area.

In the summer of 2014, São Martinho attracted many curious people due to have been visited by a seal, probably coming from France, England or Iceland. The animal became known as "Martinha" and was, in that summer, the "mascot" of the village.