| Province: | QC |
| Type: | Autoroute |
| Route: | 31 |
| Alternate Name: | Autoroute Antonio-Barrette |
| Maint: | Transports Québec |
| Map Custom: | yes |
| Map Notes: | A-31 highlighted in red |
| Length Km: | 14 |
| Length Round: | 1 |
| Length Ref: | [1] [2] |
| Direction A: | South |
| Terminus A: | in Lavaltrie |
| Direction B: | North |
| Terminus B: | in Joliette |
| Previous Type: | A |
| Previous Route: | 30 |
| Next Type: | A |
| Next Route: | 35 |
| Cities: | Joliette, Lavaltrie, Saint-Thomas |
| Established: | 1966 |
Autoroute 31 (A-31) is an Autoroute in the region of Lanaudière in Quebec. Constructed in 1966, A-31 primarily links Joliette with A-40 and in turn to Montreal, Trois-Rivières, and other points served by Quebec's autoroute system. A-31 is only 141NaN1 long, making it one of the shortest autoroutes in the province. It is multiplexed with Route 131 for its entire length.
A-31 carries the name Autoroute Antonio-Barrette, named for a politician from Joliette who briefly served as Premier of Quebec in 1960.
A-31 begins just south of its interchange with A-40 in Lavaltrie. Motorists exiting A-40 can choose to head north on A-31/Route 131 or south on Route 131 alone to Lavaltrie's city centre. The A-31/A-40 interchange has an unusual configuration, built to accommodate tollbooths that were dismantled.
The freeway runs through farmland for much of its length, with exits at km 2, km 7 and km 12 to serve local roads.
A-31 ends at km 15 at a cloverleaf interchange with Route 158. Plans for Quebec's autoroute system initially called for A-31 to meet A-50 at this interchange. Anticipating this outcome, Route 158 in the immediate vicinity of the interchange was constructed as a limited-access highway and signed as A-50. Once plans to extend the A-50 east of the A-15 were abandoned in the 1980s, this stretch of highway was redesignated Route 158. A series of deadly accidents on Route 158 prompted a 2014 petition drive to reconstruct the highway to Autoroute standards and return the designation of A-50.[3]
Motorists exiting A-31 at km 15 may continue on Route 158 west to Saint-Esprit, Route 158 east to Berthierville, or Route 131 north to Saint-Félix-de-Valois. Past this interchange, A-31 ends and becomes Boulevard Dollard, which continues into downtown Joliette.