Portrunny Harbour sits on the western shore of Lough Ree in County Roscommon, sheltered within the naturally occurring Portrunny Bay between Cruit Point and Rinanny Point.

Lough Ree is the second largest lake on the River Shannon and stretches nearly 30 km from Lanesborough to Athlone. The bay's water depth ranges from around 60 cm to an average of 6 m, making it well suited for recreational boats and cruisers.

The harbour includes a modern mooring facility and a slipway providing access to the lake. The surrounding amenity area features picnic tables, a children's playground, sanitary facilities, and car parking.

The site falls within a Special Area of Conservation, preserving its natural shoreline and habitat. It is a popular destination during summer months.