The Swilly is named after a monster. An tSúileach means something close to ‘the many-eyed one’, from a legend that a man-eating water beast with countless eyes haunted the river until Saint Colmcille killed it. The story still does the rounds locally. The river rises on Glendore Mountain in west Donegal and runs roughly 42 km east through Letterkenny before it empties into Lough Swilly.
Be clear about what you’re coming to see. Through Letterkenny the Swilly is a working town river, not a beauty spot; the interest is in the history stacked along its banks, not the water itself. Keep to public streets and paths around Letterkenny and stay back from the river in high water.
The bridges
Four bridges span the Swilly in Letterkenny, each from a different chapter of the town:
- Oldtown Bridge – the old stone crossing that was the town’s original link over the river.
- Port Bridge – a later road bridge near the site of the former commercial port.
- Rail Bridge – a relic of the closed railway that once tied Donegal into the national network.
- Devlin Way – the first pedestrian-only bridge over the Swilly, opened in November 2006. Designed by TS McLaughlin Structural Engineers and built by Bonnar Engineering, the crossing has a maroon cambered steel deck, cast-iron lamps and a commemorative stone seat. It is named for the Devlin family, who gave part of their land to make it possible.
A working river
A canal was once meant to run from here. In the mid-1700s a scheme was floated to link the Swilly with the River Foyle by canal; it never got built. What did happen was smaller. From the 17th century the river was a crossing point for the growing settlement, and by the 1800s and early 1900s a modest shipping trade worked its narrow, bending channel, carrying coal and farm produce. The port closed in the 1960s when the channel proved too awkward to navigate, and the warehouses came down in 2001. The old coal yard still stands opposite the Mount Errigal Hotel.
Upstream, the river’s current was put to work, and its water powered the corn and flax mills at Newmills, where a large waterwheel drove the machinery. The OPW lists the 2026 visitor season as ending on 4 October. Check its notice for the next opening before you go.
Fishing
Inland Fisheries Ireland lists the Swilly as closed to fishing for salmon and sea trout over 40 cm in 2026. Check the current rules and permissions with Inland Fisheries Ireland before any fishing trip. Don’t assume the banks are open to anglers.