Altomünster Abbey, Benedictine monastery in Altomünster, Bavaria, Germany

Altomünster Abbey is a former Bridgettine double monastery in Altomünster, Bavaria. Its church, rebuilt in late Rococo style by Johann Michael Fischer from 1763 to 1766, has a central plan for the parish and a long, narrow choir with four separate zones for nuns, monks, diocesan priests and priests of other orders. The complex includes an octagonal building with a steep red-tiled pyramidal roof and a tower under scaffolding.

Saint Alto, a monk of Irish origin, founded a hermitage here before 760. Around 970 the Welfs renewed it as a Benedictine monastery; in 1056 Welf I moved its monks to Weingarten and nuns from Altdorf took their place. In 1496 Duke George the Rich granted the Bridgettines of Maihingen a monastery, and the community was dissolved in 1803 and again in January 2017.

The abbey church, rebuilt 1763–1766 by Johann Michael Fischer, is dedicated to Saints Alto and Birgitta. Its long, narrow choir has four separate zones for nuns, monks, diocesan priests and priests of other orders, a layout required by the Bridgettine rule. The Bridgettine library held about 80 percent of all known Bridgettine books before passing to the Munich diocese in 2017.

The abbey closed in January 2017, so the church of Sankt Alto and Sankt Birgitta is no longer a convent church but serves the parish; the former convent buildings are not open as a living monastery. The Museum Altomünster, next to the abbey since 1997, documents the Bridgettine order. The complex stands in the centre of the market town, and the tower is currently wrapped in scaffolding netting.

The abbey library held around 80 percent of all known Bridgettine books when the monastery closed in 2017; the collection passed to the Munich diocese. Two 12th-century gospel lectionaries made for the abbey are kept today by the Bavarian State Library.