Wleń [vlɛɲ] (German: Lähn) is a small historic town in Lwówek Śląski County, Lower Silesian Voivodeship, in south-western Poland.

It is located on the Bóbr river in the historic Lower Silesian region, approximately 13 kilometres (8 mi) south-east of Lwówek Śląski, and 97 kilometres (60 mi) west of the regional capital Wrocław.

Wleń was established in 1214 by the Silesian duke Henry I the Bearded and his wife Hedwig of Andechs, as part of fragmented medieval Poland.

It was located near the Wleń Castle, one of the oldest castles in Poland, which served as a seat of a castellany that was probably founded in 1108 by Polish ruler Bolesław III Wrymouth.

As a result of further fragmentation of Poland into smaller district principalities, Wleń formed part of the duchies of Legnica and Jawor.