Lough Key is a large lake in County Roscommon, in the west of Ireland, situated within the Shannon Navigation system. Despite its considerable size, the lake appears smaller than it is due to the roughly 32 islands scattered throughout its waters, which create a varied and visually interesting paddling environment with hidden inlets and sheltered passages between landmasses.

The lake connects to the broader Shannon waterway on its eastern side, giving paddlers access to the longest river in Ireland and the UK. To the west, the Boyle River exits the lake and flows toward County Sligo, with onward access to Lough Gara. The route between Lough Key and Carrick-on-Shannon, approximately 15 minutes away by car, is considered one of the more popular waterway journeys in the area.

Kayaking is available through P Mac's Kayak Excursions, which operates within Lough Key Forest and Activity Park on the lake's southern shore. The park also has a slipway at the main car park where paddlers can launch their own boats, and a marina where visiting boaters can moor. Buoyancy aids are required when using the slipway. The park's visitor centre, lakeside café, and campsite provide useful amenities for paddlers spending extended time in the area.

Drummans Island, accessible via a high bridge from the shore trail, offers piers and sheltered spots along its approximately 1.5 km perimeter. The shoreline path within the forest park hugs the lake for much of its length, with old piers and viewpoints accessible from the water's edge. The lake and its surroundings include historic buildings and sites of cultural interest.

Swimming in the lake is not recommended by park management, as there are no lifeguards on duty. Anyone entering the water does so at their own risk. Irish statutory regulations require that persons under 16 not operate personal watercraft or fast power craft, and those under 12 not operate any engine-powered craft above 5 horsepower. Appropriate personal flotation devices are required for those on open or decked craft.