Lough Gowna (Irish: Loch Gamhna, meaning "calf lake") is a freshwater lake straddling the border between County Longford and County Cavan, with the largest portion lying in County Longford. It sits roughly 12 km north-west of Longford town and forms the uppermost lake on the River Erne system. The lake is moraine-dammed, a product of the last glaciation, and its complex, indented shape reflects the underlying drumlin landscape. This geology produces a large number of bays, inlets, and basins connected by narrow channels, giving paddlers an intricate shoreline to explore. The interconnected basins collectively form part of what are known as the Gowna Lakes, the headwaters of the Erne.

The lake is quite shallow overall, with depths averaging between 2 and 8 metres, though the southern section near Dring reaches depths of up to 15 metres. The River Erne enters the system from the east into the portion locally known as Derries Lough and exits northward through County Cavan. Several other small rivers also feed the lake.

Multiple public launch sites with gravel slipways provide good access for kayaks and paddle-boards. On the Longford side, Dernaferst (approximately 3 km south-west of Gowna village) offers a car park and public amenity area with launch points on both the north and south shores; the two basins here are connected by a narrow, shallow channel that is navigable except at the lowest summer water levels. Lisanny, located 3.5 km from Gowna village off the road toward Ballinagh, features a car park and launch area and is notable for its greater extent of emergent vegetation such as reeds and rushes. Dring, in the southern part of the lake, is another established launch point. On the Cavan side, slipways are available near Cloone, Aghanoran, and Corfree.

The lake's sheltered bays and the absence of heavy commercial boat traffic mean paddlers can navigate the shoreline and reach Inchmore Island with considerable solitude. The surrounding landscape is rich in birdlife, including whooper swans and great crested grebes, consistent with the broader drumlin lake complex of the upper Erne. The area falls within Ireland's Hidden Heartlands designation. The nearby villages of Ballinalee and Aughnacliffe offer car parks, public restrooms, and cafés for those seeking additional amenities before or after a paddle.