Ilsenburg is a town in the district of Harz, in Saxony-Anhalt in Germany. It is situated under the north foot of the Harz Mountains, at the entrance to the Ilse valley with its little river, the Ilse, a tributary of the Oker, about six 6 miles north-west of the town of Wernigerode. It received town privileges in 1959. Owing to its surrounding of forests and mountains as well as its position on the edge of the Harz National Park, Ilsenburg is a popular tourist resort. Since 2002, it is officially an air spa.