Waldeck (or Waldeck-Pyrmont) was a sovereign principality in what is now Lower Saxony and Hesse (Germany).

Waldeck was a county within the Holy Roman Empire from about 1200. Its seat shifted from the castle and small town of Waldeck, overlooking the Eder river, to Arolsen after the counts were elevated to princes in 1712. In 1625 the principality of Pyrmont became part of the county. The independency of the principality was confirmed in 1815 by the Congress of Vienna.

In 1867 the administration was taken over by Prussia. It was absorbed into the German Empire in 1870, and the principality was abolished in 1918, when it became the state (Freistaat) Waldeck-Pyrmont of Germany. In 1922 the city of Pyrmont left the district, when its population decided in a plebiscite to join the Prussian province of Hanover (now Lower Saxony). 1929, after another plebiscite, the remaining territory was annexed by Prussia as well; it became part of the province of Hesse-Nassau (now Hesse).

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