| Province: | QC |
| Type: | QC |
| Route: | 342 |
| Maint: | Transports Québec |
| Map: | Route 342-QC.png |
| Length Km: | 36.5 |
| Length Round: | 1 |
| Length Ref: | [1] |
| Direction A: | West |
| Direction B: | East |
| Terminus A: | Chemin Grande Montée in Pointe-Fortune |
| Terminus B: | in Vaudreuil-Dorion |
| Previous Type: | QC |
| Previous Route: | 341 |
| Next Type: | QC |
| Next Route: | 343 |
| Counties: | Vaudreuil-Soulanges |
| Cities: | Rigaud, Hudson, Vaudreuil-Dorion |
| Junction: | in Pointe-Fortune in Rigaud in Hudson in Saint-Lazare in Vaudreuil-Dorion |
Route 342 is a provincial highway located in the Montérégie region of Quebec west of Montreal. It runs from the Ontario-Quebec border in Pointe-Fortune (at the junctions of Ontario Highway 417 and Autoroute 40 and ends in Vaudreuil-Dorion at the junction of Autoroute 20. Before the construction of Autoroute 40 in 1959 (and its continuation in Ontario as Highway 417) it was the main route between Montreal, Quebec and Ottawa, Ontario (becoming Route 17 in Ontario). It serves as an alternate route to Autoroute 40 and has 4 interchanges with it in Pointe-Fortune, Rigaud and Hudson.
| RCM or ET | Municipality | Km | Junction | Notes | |
|---|---|---|---|---|---|
| Vaudreuil-Soulanges | Pointe-Fortune | 0.0 | Chemin Grande Montée (Prescott-Russell County Road 14) | SOUTH: to East Hawkesbury, Ontario and EAST (Exit 1), Montreal NORTH: to Pointe-Fortune | |
| 0.4 | (Exit 1) | 40 WEST: to and East Hawkesbury, Ontario | |||
| 2.3 | Chemin des Outaouais | NORTH: to Pointe-Fortune | |||
| Rigaud | 8.1 8.9 | (Exit 9) | 40 EAST: to Montreal 40 WEST: to Pointe-Fortune | ||
| 9.9 | (North end) | 325 SOUTH: to Très-Saint-Rédempteur | |||
| 11.1 11.4 | (Exit 12) | 40 EAST: to Montreal 40 WEST: to Pointe-Fortune | |||
| 16.6 | 201 SOUTH: to Salaberry-de-Valleyfield 201 NORTH: to Hudson | ||||
| Hudson | 21.6 | Cote-Saint-Charles | SOUTH: to (Exit 22) & Saint-Lazare | ||
| Vaudreuil-Dorion | 26.4 | Chemin Daoust | SOUTH: to (Exit 26-E) & Saint-Lazare | ||
| 27.3 | (Exit 26-W) | 40 EAST: to Montreal | |||
| 32.1 | 340 EAST: to Vaudreuil-Dorion 340 WEST: to Saint-Lazare | ||||
| 36.4 36.5 | |||||