Strangford Lough is a large (150km²) shallow sea lough situated on the east coast of County Down, Northern Ireland

The Lough's northern tip is only about 6 km from the outskirts of Belfast.

About a third of the Lough is intertidal - best seen from the huge expanses of sandflats exposed at the northern end at low tide. At high tide this area is covered in shallow water.

The southern entrance to the Lough is a deep channel about 8km long, called the Narrows. From Portaferry across the Narrows to Strangford is just 0.5km. The currents in between are extremely strong and fast - up to 8 knots (4m/s).