The monastery of rein – Cistercian monastery located near Gratwein in Austria's Styria. The monastery is also known as the "cradle of Styria".

The monastery was founded in 1129 by Leopold Strongest of Styria, was moved by the monks from the Abbey of the Ebre (Bavaria) under the direction of the first Abbot of Gerlachs. At that time it was a .38 Cistercian monastery, however, the previous 37 is not preserved and this means that Ryan is the oldest surviving monastery of the Cistercians.

In September 1276 noble citizens of Styria and Carinthia entered into an Alliance with king Rudolf I against the ruling of king Ottokar II, facilitated the consolidation of Habsburg as rulers of Austria.

In the 15th century the monastery was at its peak. However, in 1480 after the Turkish invasion, the monastery was badly damaged. The lesions were eliminated in subsequent years, built fortifications with ramparts and towers. In the same year, an outbreak of plague, which killed the Abbot fell Ganser (1472-1480).

In the early 17th century came the need for expansion of the monastery buildings. Changes were made in 1629-1632 years by the architect Bartolomeo di Bosio. Restoration of the Church in Baroque style was made 1738-1747, Johann Georg Stenham from Graz. The frescoes, which appeared in 1766, was made by Joseph Adam von MOLCOM, and dossal Katina - Martin Johann Schmidt in 1779.

The Abbey library consisting of 100,000 books, contains 390 unique manuscripts.

During the Second world war the Abbey was confiscated by the Nazis, and the monks expelled. Back they were able at the end of 1945. Currently the Abbey has 10 and the Abbot of Steigenberger Petrus (56th Abbot since the Foundation of the monastery).