| Province: | NL |
| Type: | NL |
| Route: | 503 |
| Alternate Name: | Grenfell Drive |
| Map: | Labrador Provincial Routes.jpg |
| Map Notes: | Route 503 highlighted in blue |
| Maint: | Newfoundland and Labrador Department of Transportation and Infrastructure |
| Length Km: | 5.2 |
| Direction A: | South |
| Terminus A: | Snow’s Drive / Bowater Drive in Wabush |
| Direction B: | North |
| Terminus B: | in Wabush |
| Previous Type: | NL |
| Previous Route: | 500 |
| Next Type: | NL |
| Next Route: | 510 |
Route 503, also known as Grenfell Drive, is a 5.2adj=midNaNadj=mid north–south highway in the Labrador West region of southwestern Labrador. It connects Wabush with the Trans-Labrador Highway and the town of Labrador City.
Route 503 begins in Wabush's southern neighbourhoods at an intersection between Snow's Drive and Bowater Drive as a two-lane highway. It heads northwest through neighbourhoods before passing along the western side of downtown, where it temporarily widens to a four-lane divided highway. The highway now narrows back to two-lanes and passes north through wooded areas before passing by an industrial/business district and the Wabush Airport before Route 503 comes to an end at an intersection with Route 500 (Trans-Labrador Highway) near Labrador City.