Belfast Lough (Irish: Loch Lao) is a large sea inlet on the east coast of Northern Ireland.

Belfast Lough is a long, wide and deep expanse of water, virtually free of strong tides.

[4][5] In 1689 during the War of the Two Kings the Williamite expeditionary force under Marshal Schomberg landed at Bangor, after the lough had been cleared of French shipping by George Rooke.

The following year William III also used the lough as a safe anchorage when he arrived in Ireland with reinforcements for Schomberg in the run-up to the victory over the Jacobite army at the Battle of the Boyne.

The site qualifies under Criterion 3c of the Ramsar Convention by regularly supporting internationally important numbers of common redshank in winter.

[10][11][12] Popular for sailing, the lough has three marinas: one at Bangor, one at Carrickfergus and a third located at Titanic Quarter.

Belfast docks at the head of a lough contain the famous shipbuilder of the RMS Titanic fame, Harland & Wolff, who are no longer building ships for the foreseeable future and has shed most of its workforce and diversified into repairing and refitting large tankers and oilrigs.

[citation needed] The lough has 30 square miles (78 km2) of open water and enough coastline to make short inshore races day-long affairs.