Sligo Harbour is a large open estuary harbour accessed via Sligo Bay, with inner areas well protected by sandy islands.

It is one of only two operating ports on Ireland's northwest coast between Galway and Derry, capable of accommodating vessels up to 100 metres in length with a maximum draft of 5. 2 metres. The port itself extends 1. 3 kilometres from the Timber Jetty.

Within the harbour, a pontoon at Ballast Quay offers moorings close to the town centre, suitable for day trips or longer stays.

In quieter weather, temporary anchorage on sand is possible off the Yacht Club at Deadman's Point, or in depths of five to six metres in the reach between Oyster Island and Rosses Point.

Sligo Bay has a long maritime history, with the area believed by some to correspond to a location marked on Ptolemy's second-century map of the world.