|To:||Bunnamayne (border) (C405212)|
|Length:||43.8 km (27.2 miles)|
|Meets:||N15, R236, N14, R237, R238, A2|
|Route outline (key)|
It starts at a junction with the N15 in Stranorlar and runs north to the edge of the River Swilly where it meets the N14 at the Dry Arch Roundabout. It doesn't quite reach Letterkenny but instead heads round to the east of the river as it flows into Loch Swilly, multiplexing with the N14, which then branches off southeast to Lifford and Strabane. It then runs along the northeast edge of the Loch, before turning inland and becomes the A2 as it passes into County Londonderry.
The N13 originally ended in Letterkenny, with the section to Stranorlar forming part of the N56. This was changed in 1993. The only other notable change to the N13 is a new build road along the N14 multiplex.