| Province: | QC |
| Type: | QC |
| Route: | 203 |
| Maint: | Transports Québec |
| Map: | Route 203-QC.png |
| Length Km: | 28.5 |
| Length Round: | 1 |
| Length Ref: | [1] |
| Direction B: | North |
| Direction A: | South |
| Terminus B: | in Très-Saint-Sacrement |
| Terminus A: | in Mooers, New York |
| Previous Type: | QC |
| Previous Route: | 202 |
| Next Type: | QC |
| Next Route: | 204 |
| Counties: | Le Haut-Saint-Laurent |
| Junction: | in Havelock in Saint-Chrysostome |
Route 203 is a provincial highway located in the Montérégie region of Quebec south of Montreal. The highway starts from the Canada–United States border south of Havelock at the north end of County Road 10 at Cannon Corners at the Cannon Corners-Covey Hill Border Crossing in Mooers, NY. From there, it proceeds north toward Saint-Chrysostome, from there it follows the north shore of the Rivière des Anglais until it connects with Route 138 in Très-Saint-Sacrement just northeast of the enclaved municipality of Howick.