| Province: | QC |
| Type: | QC |
| Route: | 321 |
| Maint: | Transports Québec |
| Map: | Route 321-QC.png |
| Length Km: | 85.7 |
| Length Round: | 1 |
| Length Ref: | [1] |
| Direction A: | South |
| Direction B: | North |
| Section1: | Papineau section |
| Length Km1: | 52.6 |
| Terminus A1: | in Papineauville |
| Junction1: |
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| Terminus B1: | Rue Principal in Duhamel |
| Section2: | Antoine-Labelle section |
| Length Km2: | 33.1 |
| Terminus A2: | Chemin Chapleau in Nominingue |
| Junction2: | in Rivière-Rouge |
| Terminus B2: | Chemin des Îles in L'Ascension |
| Previous Type: | QC |
| Previous Route: | 317 |
| Next Type: | QC |
| Next Route: | 323 |
| Counties: | Papineau, Antoine-Labelle |
Route 321 is a regional road in Quebec, Canada, that consists of two unconnected sections: one in Papineau Regional County Municipality that runs from Papineauville to Duhamel, and a second section of the road goes from Nominingue to L'Ascension in the Antoine-Labelle Regional County Municipality; there's 67 to 72 km in between (depending on the route).
The portion north of Chénéville in Papineau RCM is still unmarked on some maps, but it is signed on the road, and is very sinuous. On most of the Chénéville-Duhamel part, it is impossible to reach the 90 km/h speed. In fact it is most of the time a 50–70 km/h speed limit road. It is frequented by campers who go to the Lac Simon recreational center during the summer.