Arnstadt is a town in Ilm-Kreis, Thuringia, Germany, on the river Gera about 20 kilometres (12 mi) south of Erfurt, the capital of Thuringia. Arnstadt is one of the oldest towns in Thuringia, and has a well-preserved historic centre with a partially preserved town wall. The town is nicknamed Das Tor zum Thüringer Wald because of its location on the northern edge of that forest. Arnstadt has a population of approximately 27,000.

Thuringia, officially the Free State of Thuringia, is a state of central Germany, covering 16,171 square kilometres (6,244 sq mi), the sixth smallest of the sixteen German states. It has a population of about 2.1 million.