Route 91 is a numbered State Highway running 12.0 miles (19.3 km) in Rhode Island.

Route 91 takes the following route through the State:

The town of Westerly and the State of Rhode Island have conflicting information on the western terminus of Route 91.

The disagreement begins at the intersection of Tower Street and Oak Street. State maintenance leaves Oak Street here and heads down Tower Street to U.S. Route 1. Because of this, the State considers Route 91 to go this way, ending at U.S. Route 1. The Town, on the other hand, considers Route 91 to stay straight on Oak Street (maintained by the Town at this point), ending at Route 3. The Town's route is shown in this article since the Town appears to be the only one who has put up signage: