The Webb River begins at the outlet of Webb Lake near the southern border of the town of Weld and flows south, quickly entering the town of Carthage, where it turns southwest, then south again.

The southernmost 6 miles (10 km) of the river forms the boundary between the towns of Mexico and Dixfield.

The river enters the Androscoggin just west of the village of Dixfield.

The entire course of the river is paralleled by Maine Route 142.

This article related to a river in Maine is a stub.