Illmitz (Hungarian: Illmic) is a market town in the district of Neusiedl am See in Burgenland in Austria. It is located in a region to the east of the Lake Neusiedl (German: Neusiedlersee; Hungarian: Fertő tó) which is named the Seewinkel (lake corner).
Illmitz is in the Neusiedler See-Seewinkel National Park on the eastern shore of Lake Neusiedl. The town is at an elevation of 117 meters above sea level. Nearby, an area 114 m (374 ft) above sea level is the lowest elevation of Austria. Characteristic of the area are wide open plains and salt marsh flora, with many small salt lakes around. The Lange Lacke (Long Lake) is the largest of about forty such lakes nearby.
In 1897, the Austrian Empire was dissolved, and Austria-Hungary was formed, with separate governments in Vienna and Busapest. After the First World War, Burgenland was named Deutsch-Westungarn (German-West Hungary) in the 1919 Treaty of St. Germain and the Treaty of Trianon and was awarded to Austria in 1919. Since 1921, the town has been part of the newly founded State of Burgenland. In December 2001, the National Park Neusiedlersee was named a UNESCO World Heritage Site.