Cork Harbour (Irish: Cuan Chorcaí) is a natural harbour and river estuary at the mouth of the River Lee in County Cork, Ireland. It is one of several which lay claim to the title of "second largest natural harbour in the world by navigational area" (after Port Jackson, Sydney). Other contenders include Halifax Harbour in Canada, and Poole Harbour in England.
The harbour has been a working port, and a strategic defensive hub, for centuries, and it has been one of Ireland’s major employment hubs since the early 1900s. Traditional, heavy, industries have waned in recent years, with the likes of the closure of Irish Steel in Haulbowline and shipbuilding at Verolme. It still has major and strategic significance in energy generation, shipping, refining and, most importantly, pharmaceuticals.
Cork City is located slightly upstream on the River Lee on the northwest corner of Cork Harbour. Several of the city's suburbs, including Blackrock, Mahon, Douglas, Passage West and Rochestown lie on Lough Mahon or the Douglas Estuary, both of which are parts of Upper Cork Harbour.