Bishop Altmann of Passau is the only bishop venerated as a saint in the former great diocese of Passau, whose territory included the present-day dioceses of Passau, Linz, St. Pölten and Vienna.
Born in Westphalia around 1010/1020, he came from an important, widely connected family of counts and was appointed Bishop of Passau as imperial court chaplain by Empress Agnes in 1065. He had previously taken part in a major pilgrimage to the Holy Land.

In 1072 Altmann consecrated the church of St. Erentrudis on Göttweig Mountain, where a wooden church of St. George had stood since the 9th century. He had received the Paudorf estate, which included the mountain, from the Formbach family from Radlberg, who were related to him, and had obviously previously been part of the large Salzburg estate, which stretched from the Arnsdörfer in the Wachau region via Wölbling to Traismauer.
Mount Göttweig has been inhabited in phases since 2,000 BC, as archaeological finds prove.

In 1083 Altmann founded Göttweig Abbey as a double monastery, which lived according to the rule of St. Augustine for the first eleven years and adopted that of St. Benedict in 1094.
He dedicated the monastery church on the mountain to Mary, the Mother of God, and the convent church in the Fladnitz Valley to St. Blaise. His friend and metropolitan, Archbishop Gebhard of Salzburg, also consecrated the monastery church of the double monastery of Admont to St. Blasius.

Altmann's main concerns were the renewal of faith and the reform of the clergy and monasteries.
He reformed the old monasteries of St. Florian, Kremsmünster and St. Pölten, was involved in the establishment of the canon monastery of Rottenbuch and the transformation of the canon monastery of Melk into a Benedictine abbey and founded the double canon monastery of St. Nikola near Passau before Göttweig.

Altmann vehemently supported the position of Pope Gregory VII (1073-1085) in the investiture dispute, which arose over the modalities of the appointment of ecclesiastical officials, as well as in the associated church reform. He was held in high esteem by him and his successors. He was papal legate for the empire for 15 years, from 1076 until his death.
For this reason, and because of his support for the opposing king Rudolf of Rheinfelden, King Henry IV expelled him from Passau in 1078. He was never able to return to his episcopal city, where a counter-bishop was appointed. From then on, he was only able to work in the eastern part of his diocese; as legate, however, he traveled throughout the entire empire.

On September 9, 1083, the feast of St. Gorgonius (patron saint of Gorze, the origin of a Benedictine reform movement favoured by Altmann), the bishop consecrated the men's monastery church to Our Lady. Although he had close ties to the Babenbergs - Leopold II had broken away from Henry IV on his account and had therefore been defeated by the Bohemians at Mailberg in 1082 - he entrusted the Formbachers of Radlberg, who were related to him, with the bailiwick of the monastery.
At the same time, Altmann entrusted the brothers with the pastoral care of four parishes. Today, the abbey's pastoral care area comprises more than 30 parishes.

On August 8, 1091, Altmann died in the Passau court of Zeiselmauer, near Tulln, where Margrave Leopold II had his seat.
He was buried in Göttweig and his grave soon attracted pilgrimages and people seeking help; the first came from Tulln.
Today, Altmann's relics are kept in a precious baroque shrine in the crypt of the collegiate church.

In order to lend stability to Göttweig, which had been founded as a monastery in Passau (an opposite bishop still ruled in Passau), it was converted into a Benedictine abbey after the death of Altmann, who was a great supporter of the canons' movement.

The first abbot in 1094 was the prior of St. Blasien, Hartmann (+1114), who had previously been provost of St. Nikola and chancellor to the counter-king Rudolf and who, for reasons of church politics but completely against the ecclesiastical reform spirit of his time, was also abbot of St. Lambrecht in Styria, of St. Ulrich and St. Afra in Augsburg and of Kempten in the Allgäu.

The nave of the collegiate church and the recently uncovered foundation walls of the church of St. Blasien in Klein-Wien date back to Bishop Altmann's time.

The holy bishop is commemorated twice a year: on August 8, the day of his death, and on June 16, the day of his translation (Duke Rudolf the Founder had Altmann's remains raised and reburied in 1362).

Göttweig's importance increases rapidly. New monasteries are settled from here: Garsten in 1107 and Seitenstetten in 1116.
A list of convents recorded in the Seckauer Verbrüderungsbuch names Abbot Johannes (1557-1174), 17 monks and 21 nuns.

Around 1250, the nunnery, whose most important nun and founder was Duchess Gerbirg (+1042), a sister of Margrave Leopold the Saint, was relocated to Göttweiger Berg. The Inklusin Ava (+1127), the first female poet in the German language, is also said to have lived in its vicinity.
In the 12th century, Austrian annalistics began in Göttweig. The “Vita Altmanni” in particular, as well as other books written here, are valuable medieval historical sources today.

In 1382, the Göttweig abbot received the pontificals, and in 1401 the monastery was “exempted”, meaning that it was no longer subject to the bishop but directly to the Holy See.

The second major construction period began in the 15th century, much of which can still be seen today: the crypt and choir of the abbey church, part of the cloister and the castle as well as the choir of St. Blasien church.
The parish church of St. Gotthard, which was completely rebuilt at the time, fell victim to the abbey fire in 1718. It was replaced by the parish church of St. Altmann in Paudorf, which was consecrated in 1993. In the meantime, the abbey church was also a parish church.

From 1418, the monastery was renewed internally by joining the Melk Reform. Nevertheless, the number of monastery members continued to decrease, debts grew, the teachings of Martin Luther and other reformers brought confusion and helplessness, and the Turkish threat became ever greater. 
Under Abbot Matthias von Znaim (1516-1532), the convent was fortified and was able to withstand the Turkish invasion of 1529, when 6,000 soldiers besieged the convent without success.
In 1514, the convent still had 18 monks and 15 nuns.  

After the death of Abbot Leopold Rueber in 1556, there was only one monk left in the house, the convent was at an end and was placed under the control of the provost of Herzogenburg, Bartholomäus a Cataneis. In 1557, he closed the women's convent, which still consisted of seven nuns, and moved it to St. Bernhard near Horn, where the last nun died in 1582. From 1508, this convent had a feminized Benedictine Rule in Middle High German, which was first printed in 1992.

The Göttweig convent was probably the oldest and longest existing women's convent of a Lower Austrian double monastery. Apart from the special case of Geras-Pernegg, the church of St. Blasien is the only surviving convent church of a double monastery in Lower Austria.

In 1564, the Benedictine Michael Herrlich (1564-1603) from Melk was appointed as the new abbot - today he is regarded as the second founder of the monastery. Despite economic hardship (monastery fire in 1580, Reformation period, plague, small number of monks), he saved the continuity of the monastery during his almost 40-year term of office.