Slieve League, Mountain with sea cliffs in County Donegal, Ireland.

Slieve League (Sliabh Liag, 'mountain of stone pillars') is a 601-metre mountain on the Atlantic coast of County Donegal. Its sea cliffs, the second-highest in Ireland after Croaghaun, drop as a layered grey-brown rock wall scored by vertical gullies, with pale sandy coves at the waterline and green grass on the upper slopes. A lower rocky headland juts into the sea near the northern end.

On the summit, protected by a semicircular stone wall, stand a ruined beehive hut and the remains of a chapel: the hermitage of Saint Áed mac Bricc, who died in 589. Pilgrims climbed to it until about 1909. A holy well lies under a stone cairn around a cross-stone outside the wall, with a second well further east.

The name Sliabh Liag means 'mountain of stone pillars' in Irish. On the summit, a semicircular stone wall shelters a ruined beehive hut and the remains of a chapel, the hermitage of Saint Áed mac Bricc, who died in 589. Pilgrims climbed here until about 1909; a holy well lies under a stone cairn beside a cross stone outside the wall.

From Teelin a 4.5 km two-lane road climbs to a car park at Carrigan Head; higher up, Bunglass Point is reserved for permit holders, shuttle buses and vehicles for disabled visitors. The One Man's Pass is signposted from Teelin and is very narrow in places, hazardous for anyone uneasy with heights or in strong gusts. Walkers can instead take the Pilgrim's Pass from An Charraig, which leads behind the cliffs to the chapel on the summit. Boat tours to the foot of the cliffs run in summer from Killybegs and Teelin.

The northern precipice drops 1,500 feet into the coomb around Little Lough Agh, which holds most of Slieve League's alpine plants. Robert Lloyd Praeger called this the most varied group of alpines anywhere in Donegal in his 1937 memoir The Way That I Went.