Killary Harbour was gouged out by a vast glacier over 10,000 years ago, although this flooded valley is more a fjord than a harbour and extends for over 8 kilometres before reaching the open sea.
In 1903, a British naval fleet dropped anchor in Killary Harbour, so that King Edward VII and Queen Alexandra could take a sightseeing tour of Connemara. Nowadays, the waters of Killary are dotted with mussel rafts and salmon cages as commercial fin-fish and shellfish farming provide a welcome boost to the local economy.The nutrient-rich waters support a host of other fish, crustacean and marine mammals. Dolphins can be seen swimming around the Cruise vessel and sharks, conger eels and huge common skate are also present.

Stories from more recent times relate German and British submarines finding shelter in the neutral waters of Ireland during the Second World War, and stories of local fishermen sailing out to British naval vessels to register their anger by hurling stones and eggs, are only the tip of the iceberg.

The coastal path on the south side of Killary Harbour offers one of the best coastal walks in Connemara. The ‘harbour’ is actually a fjord-like sea inlet, dominated by the mountain of Mweelrea. The route uses a minor road, tracks and paths, nearly always with good coastal and mountain views. The path crosses through an old deserted settlement and was once used by the community to carry their dead to the cemetery.