Leun (German pronunciation: [lɔʏn] ^ⓘ) is a small town in the Lahn-Dill-Kreis in Hesse, Germany.

Leun lies some 10 km west of Wetzlar between the foothills of the northern Taunus and the Westerwald in the Lahn valley, at a height of 150 to 330 m above sea level.

Leun borders in the north on the communities of Greifenstein and Ehringshausen, in the east on the town of Solms, in the south on the town of Braunfels (all in the Lahn-Dill-Kreis) and in the west on the community of Löhnberg (Limburg-Weilburg).

The town consists of the five centres of Biskirchen, Bissenberg, Lahnbahnhof, Leun and Stockhausen.

Leun had its first documentary mention in 771. Building a stone bridge in the late 15th century and being granted market rights helped the village's economic growth, which in 1664 resulted in town rights being granted.

As part of Hesse's municipal reform, the new, bigger town of Leun came into being when the main town of Leun and the other aforesaid communities voluntarily joined together on 1 January 1972.

The municipal elections on 6 March 2016 yielded the following results:

Note: FWG is a citizens' coalition.