Niedenstein (German: [ˈniːdnˌʃtaɪ̯n] ⓘ) is a small town and an officially recognized climatic spa in the Schwalm-Eder district in northern Hesse, Germany.

Niedenstein's main settlement lies to the southeast of the Habichtswald Nature Park, right on the western slope of the Langenberge, a low mountain range reaching 557 m. The nearest city is Kassel, about 15 km to the northeast.

In the north, Niedenstein abuts Schauenburg, in the east beyond the Langenberge it adjoins Baunatal and Edermünde, and in the southeast its constituent community of Metze on Gudensberg.

In the south, the constituent community of Kirchberg, through which flows the river Ems, borders on Fritzlar, whose main town lies about 11 km away from Niedenstein.

It was Konrad von Elben, ordered by Duchess Sophie, who had built the new city in 1259 on his own land in the area of Wichdorf.

(as of municipal elections held on 26 March 2006) Niedenstein maintains a partnership with one place: It lies about 80 km northwest of Paris in Picardy.