Abbaye d'Allendorf, Monastery ruin in Bad Salzungen, Germany

Kloster Allendorf is a former women's monastery in Bad Salzungen, founded after 1265 and once a place for prayer and communal life. Today, mainly the walls of the medieval church ruin remain standing and are protected as a historical monument.

The monastery was founded after 1265 by the Lords of Frankenstein, a branch of the Counts of Henneberg, on the site of an older Marian chapel mentioned that year; a 1266 indulgence from Bishop Gerhard von der Mark of Münster is the first written record. It was damaged in Adolf of Nassau's 1295 Thuringian campaigns, and in 1508 Provost Johann Löher replaced the nuns with Benedictines from St. Ulrich in Würzburg. After the Peasants' War of 1525 the Protestant rulers confiscated its property and dissolved it; a 1786 fire destroyed the buildings, whose ruins were then quarried for stone.

The monastery's name comes from the village of Allendorf across the Werra; the small settlement that grew around the buildings is today the Bad Salzungen district of Kloster. The church, consecrated in 1314 by Bishop Siegfried von Gelnhausen, served the Protestant community from 1634 until 1786. The nave is still used as a dwelling and is not open to the public.

The former monastery stands about 300 m from the right bank of the Werra on the western slope of the Frankenstein, in Bad Salzungen's Kloster district. The nave of the former monastery is still used and managed as a private residence and is not open to the public; the church ruin is likewise closed off. The site can be viewed from the outside only.

A fire in 1786 nearly destroyed the monastery buildings completely, after which the stones were reused for other construction projects in the area. Historical documents from the 14th century kept in archives record the lives of the women who lived there and show how the community changed over the centuries.