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.

The House of Schwarzburg was one of the oldest noble families of Thuringia, which is in modern-day central Germany. Upon the death of Prince Friedrich Günther in 1971, a claim to the headship of the house passed under Semi-Salic primogeniture to his elder sister, Princess Marie Antoinette of Schwarzburg who married Friedrich Magnus V, Count of Solms-Wildenfels. Reigning over the County of Schwarzburg and founded by Sizzo I of Schwarzburg, the family split in the 16th century into the lines of Schwarzburg-Sondershausen and Schwarzburg-Rudolstadt, with the Sondershausen dying out in 1909.