River Shannon: Ireland's Longest River

The River Shannon (Abhainn na Sionainne) is Ireland's longest river — 360 km (224 mi) from source to Atlantic.

Key Facts

• Source: Black Lough (Cuilcagh Mountain), County Cavan — 150 m elevation.
• Course: South through Lough Allen, Lough Ree, Lough Derg (major lakes); past Athlone, Clonmacnoise, Limerick.
• Mouth: Shannon Estuary → Atlantic at Loop Head, County Clare.
• Basin: 16,865 km² (20% of Ireland).
• Tributaries: Suck, Inny, Brosna, Little Brosna, Mulkear.

Navigation & Infrastructure

• Navigable: 240 km (Limerick to Leitrim) — 6 locks (Ardnacrusha, Roosky, Tarmonbarry, Richmond, Shannonbridge, Athlone).
• Ardnacrusha Hydroelectric Station (1929) — 86 MW; Ireland's first major infrastructure project.
• Shannon-Erne Waterway (1994) — connects to Erne system (Northern Ireland).

Ecology & Culture

• Salmon, trout, eel, lamprey; otter, kingfisher, whooper swan.
• Monastic sites (Clonmacnoise — 6th c.), Viking bases (Limerick), Norman castles.
• Literary: "The Shannon" in Yeats, Heaney, O'Brien.

The Shannon is Ireland's hydrologic, historic, and imaginative spine.