Cork Harbour 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 the United Kingdom.
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.
The Royal Cork Yacht Club – the world's oldest – is based in Crosshaven. There is another marina at East Ferry on Great Island. Small facilities at Monkstown and Blackrock are used for boating, canoeing, windsurfing and jet-skiing. A number of rowing clubs have facilities on the part of the River Lee between Cork City and Blackrock.