St. Margrethen (Saint Margrethen/Sankt Margrethen) is a town in the canton of St. Gallen is Switzerland. It is home to 5,300 inhabitants.

It is close to Austria and Germany and acts a border town with Austria.

Currently only a normal road links St. Margrethen with Austria. As a result the town is at times clogged up with traffic before the customs posts. A motorway link has long been projected, to link the pathways to Zurich and Munich.

It is also where the A1 motorway becomes the A13 motorway.