Route 103 is a 4.92-mile-long (7.92 km) east–west state highway in southeastern Massachusetts.

It begins in Swansea at the Warren line, heading eastward as Wilbur Avenue.

It crosses the Cole River before entering the village of Ocean Grove.

As the route enters Somerset it crosses the Lees River, just east of its junction with Exit 4 of I-195.

From there it continues eastward, north of Brayton Point and the Dominion Resources power station before Wilbur Avenue turns northward, intersecting with Riverside Avenue at the end of Brayton Avenue, where all three roads formerly met the Slade's Ferry Bridge.