HAINBURG, or Haimburg, a town of Austria, in the circle of Bruck, situated on the Danube 27 miles E.S.E. of Vienna, is the seat of a district court of justice and of a tax-offiae. It occupies part of the site of the old Celtic town Carnuntum, destroyed 251 a.d. Since the fire of 1827 Hainburg has been much improved, and is now a handsomely built town. It is still surrounded by ancient walls, and has a gate guarded by two old towers. There are numerous Roman remains, among which may be mentioned the altar and tower at the town-house, on the latter of which is a statue, said to be of Attila. A Roman aqueduct is still used to bring water to the town. Hainburg has a military school for engineers. The two important manufactures are tobacco, employing about 1700 hands, and needles, of which about 80 millions are annually turned out. On the neighbouring Hainberg is an old castle, built of Roman remains, which appears in German tradition under the name of Heimburc; it was wrested from the Hungarians in 1042 by the emperor Henry III. At the foot of the same hill is a castle of the 12th century, where Ottocar, of Bohemia, was married to Margaret of Austria in 1252; earlier it was the residence of the dukes of Babenberg. Outside the town, on an island in the Danube, is the ruined castle of Röthelstein or Rothenstein, held by the Knights Templars. Hainburg was besieged by the Hungarians in 1477, was captured by Matthias Corvinus in 1482, and was sacked, and its inhabitants massacred, by the Turks in 1683. Population (1869), 4178.