The Long Forties is an area of the northern North Sea that is fairly consistently forty fathoms (73 metres) deep (thus, on a nautical chart with depth shown in fathoms, a long area with many "40" notations). It is located between the northeast coast of Scotland and the southwest coast of Norway, centred about 57°N 0°30′E. Compare to the Broad Fourteens.
The Shipping Forecast area "Forties" is named after it. The Dutch weather service KNMI uses for the same area the name of the Fladen Grounds, a slightly more northernly and deeper part of the North Sea. The Swedish weather service SMHI who reported weather for this area until 2005 also used the name Fladen for this area. The Norwegian forecast for the fisheries uses the term Fladen Grunn.