Doon Hill, Extinct volcano in Bunowen More, County Galway, Ireland.

Doon Hill is an extinct volcano on the Errismore peninsula that rises about 63 meters above sea level. The volcanic plug sits near Bunowen Harbour in western Ireland and forms a distinctive landmark in the coastal landscape.

Doon Hill's summit holds the ruins of a signal tower built around 1806 during the Napoleonic era, part of a coastal warning chain. A concrete watch post was added there during The Emergency, Ireland's name for the Second World War. The hill's Irish name, Cnoc an Dúin, means hill of the fort, hinting at an earlier fortification on the same spot.

The name comes from Irish and means hill of the fort, reflecting its role as a defensive position. Local people have long recognized this spot as an important coastal landmark.

The hill is easy to spot from the coast and serves as a navigation point for fishermen approaching Bunowen Pier. The area is relatively accessible, though reaching the summit depends on local conditions.

The Irish name Cnoc an Dúin means "hill of the fort", and the element dún (fortress) hints at an earlier fort on the summit, before the 1806 signal tower. Fishermen still use the hill as a landmark to steer into Bunowen Pier at Aillebrack.