The Minster on Fraueninsel is one of the oldest Christian places of worship in southern Germany. This region was Christianized in the 7th century by Irish-Scottish wandering monks who came to this area from Scotland and Ireland and established their mission station in Salzburg.

The Irish itinerant missionary and saint, Virgil (~700-784), monk of the Scottish Abbey of Iona on the island of the same name and builder of the first Salzburg Cathedral, consecrated the monastery church of the women's monastery founded by the Bavarian Duke Tassilo III (around 741-around 796) on September 1, 782 as Bishop of Salzburg. This is documented.

Irmengard , a daughter of King Louis the German and great-granddaughter of Charlemagne, headed the monastery around 850 and died on July 16, 866 at the age of about 33. Her date of death is recorded in the Codex Sangallensis from the 9th century.
Tradition tells of her saintly life and work. This assumption is confirmed by the burial of her bones in a marble coffin under the south-west pillar of the cathedral.
Around the year 1000, when a grave was first opened, her veneration was attested to by the addition of a small lead tablet, which has been preserved to this day as valuable evidence. On Friday, October 17, 1631, Irmengard's bones were raised from her original grave.
However, historical sources remain sparse. The monastery's tradition tells of her piety, her love of God and her neighbour, and her concern for all the poor around her. She was officially beatified by Pope Pius XI in December 1928.

Until the secularization of 1803, the Frauenchiemsee Abbey belonged to the Archdiocese of Salzburg and was only then assigned to the Archdiocese of Munich and Freising.