AREMBERG or ARENBERG, formerly a German duchy of the Holy Roman Empire in the circle of the Rhine Palatinate, between Jiilich and Cologne. The hamlet of Aremberg is at the foot of a basalt hill 2,067f t. high, on the summit of which are the ruins of the original castle of the family of Aremberg.
The lords of Aremberg first appear early in the 12th century, but had died out in the male line by 1279. From the marriage of the heiress Mathilda (1282-99) with Engelbert II., count of La Marck (d. 1328), sprang two sons. The second of these, Engel bert III. (d. 1387), inherited the lordship of Aremberg which remained in his family till 1547, when it passed, by his marriage with Margaret, sister of the childless Robert III., to John of Barbancon, of the great house of Ligne, who assumed the name and arms of Aremberg, and was created a count of the Empire by Charles V. He was governor of Friesland, and for a while commanded the Spanish and Catholic forces against the "beggars," falling at the battle of Heiligerlee in 1568. His son Charles (d. 1618) greatly increased the possessions of the house by his marriage with Ann of Croy, heiress of Croy and of Chimay Aerschot, and in 1576 was made prince of the Empire by Maxi milian II. His grandson, Philip Francis, was made duke in 1644 by the emperor Ferdinand III.
Duke Prosper Louis who had lost his possessions in 1810 by an act of Napoleon, regained them in 1815 at the Congress of Vienna, which, however, mediatized them.