Frederikshald, Or Frederikshall (Formerly Halden), a seaport of Norway, in the province of Christiania, on the Iddefiord near its junction with the gulf of Swinesund, Skager Rack, 57 m. S. E. of Christiania, near the frontier of Sweden; pop. in 1865, 9,219. The harbor is excellent, and is accessible to the largest class of shipping. The great fire of 1759 nearly destroyed the town, but it has been handsomely rebuilt. It stands around the base of a gigantic rock, on the summit of which, 400 ft. perpendicularly over the sea, is the historic fortress of Frederiksteen, formerly of great strength. Charles XII. was killed here, Dec. 11, 1718. On the only accessible side, close under the outer walls, a monument marks the spot where the king fell. The castle was invested in 1814 by the Swedish crown prince Bernadotte, and its hopeless defence was a prelude to the almost immediate conquest of the kingdom and its union with Sweden, Nov. 4, 1814. About 3 m. E. of the town is a lake, the Fem So, the stream from which flows into the fiord near Frederikshald. Its waterfalls are the most picturesque in S. Norway.