Wienhausen Abbey or Convent (German: Kloster Wienhausen) near Celle in Lower Saxony, Germany, is a community of Evangelical Lutheran women, which until the Reformation was a Cistercian Catholic nunnery. The abbey owns significant artworks and artifacts, including a collection of tapestries and the earliest surviving example of a type of eyeglasses.
The abbey was established in Wienhausen, 15 kilometers (9.3 mi) from the town of Celle, on the bank of the Aller, in or about 1230 by Agnes von Landsberg, daughter-in-law of Henry the Lion, Duke of Saxony and Bavaria. According to the Wienhausen town chronicle, this was the relocation of a monastic foundation made 10 years previously on a site at Nienhagen several kilometers away, which was moved because it had been built on marshland.
In 1233 the foundation of the nunnery here was officially confirmed by Konrad II of Riesenberg, bishop of Hildesheim, who transferred to the new abbey the archdeaconry church that had stood in Wienhausen since the mid 11th century, and the tithes of several villages. The nuns lived according to the Cistercian rule although it is unclear to what extent they were ever formally part of the Cistercian hierarchy.
In 1469 the abbey came under the influence of the reformist Windesheim Congregation and were obliged to tighten up their Cistercian practice; one side-effect of the reform was that the then abbess, Katharina von Hoya, was removed to another nunnery.