Route 321 is a 25.1-kilometre (15.6 mi), two-lane, uncontrolled-access, local highway in eastern Prince Edward Island.

Its southern terminus is at Route 3 in Lot 53 and its northern terminus is at Route 2 in Morell.

The route begins at its southern terminus and heads north, crossing the Cardigan River.

It joins Route 4 for a 450-metre (1,480 ft) concurrency before continuing north.

This Prince Edward Island road, road transport or highway-related article is a stub.