(also Isafjardardjúp), a bay on the Atlantic, cutting into the northwestern coast of Iceland for a distance of 74 km.
The bay is 22 km wide at the entrance, and its depth ranges from 20 to 91 m, reaching 128 m in the central part. The bay’s rocky and rugged shoreline is dissected by many lateral fjords. It has semidiurnal tides, rising to a height of 3 m. From October through June the bay is covered with floe ice brought by currents. The city of Isafjordur lies on the southern shore of the bay.