Route 138 is a numbered State Highway running 48.3 miles (77.7 km) in Rhode Island. It is the longest state numbered route in Rhode Island, and the second longest highway after US 1. Route 138 begins in Exeter at the Connecticut state line in the west and runs to the Massachusetts state line in Tiverton in the east, and is the only state-numbered route to completely cross Rhode Island. Route 138 also keeps the same route number on the other side of both state lines.