JADE or JAHDE, a deep bay and estuary of the North Sea, belonging to Oldenburg. The bay, which was for the most part made by storm-floods in the i3th and i6th centuries, measures 7o sq.m., and has communication with the open sea by a fairway, m. wide, which never freezes, and with the tide gives access to the largest vessels. On the west side of the entrance to the bay is the port of Wilhelmshaven. A stream, about 14 m. long, also known as the Jade, enters the head of the bay.