Route 81 is a short 2.61-mile-long (4.20 km) south–north state highway located entirely within the city of Fall River, Massachusetts.

It begins as a continuation of Rhode Island Route 81 and ends at an interchange with I-195.

Prior to the 1960s, much of what is now William S. Canning Boulevard did not exist, as the route passes through former wetlands around the Sucker Brook.

Form there it proceeds northward, past the SouthCoast Marketplace (formerly the New Harbour Mall) and Fall River Shopping Center.

The entire route is in Fall River, Bristol County.