Provincial Road 321 (PR 321) is a 31.9-kilometre-long (19.8 mi) east–west highway in the Winnipeg Capital Region of Manitoba, Canada.

It connects the towns of Grosse Isle and Stony Mountain with Parkdale on the north side of Winnipeg.

PR 321 begins in Grosse Isle at an intersection with PTH 6 (Northern Woods and Water Route) along the border between the Rural Municipality of Rosser and the Rural Municipality of Rockwood.

It heads east through the centre of town, crossing the Prairie Dog Central Railway before having a junction with PR 322 (Road 1E), where the pavement turns to gravel.

Leaving Grosse Isle behind, it continues east through rural farmland for several kilometres along Road 72N, crossing a small creek and PR 236.