The Koutloumousiou Monastery is located near Karyes on Mount Athos and dedicated to Christ the Savior. Although a forged document in its archives claims that Alexios I founded Koutloumousiou in 1082, the monastery is first mentioned in a document of 1169, and appears to be a 12th-century foundation. The monastery's unusual name, derived from the Turkish patronymic Kutulmuş, suggests that a Christianized descendant of the Seljuk prince Kutulmuş (died 1063) may have retired to Athos and established a monastic complex. The monastery was small and poor in resources until the 14th century when it increased to 40 monks and acquired substantial properties in Macedonia (near Serres and on Chalkidike) and in Wallachia. It reached its peak under the hegoumenos Chariton (c. 1362 - c. 1381), who attracted the patronage of Wallachian voivodes, which was to continue well into the period of Turkish rule. As a concession to the Wallachian monks who came to reside at Koutloumousiou, Chariton was forced around 1371 to institute an idiorrhythmic regime that lasted until 1856. In 1393 Koutloumousiou became a patriarchal monastery. In 1428 the monks of Koutloumousiou took over the virtually abandoned buildings of the nearby monastery of Alopou (Alypiou). Thereafter, the two monasteries were united under one hegoumenos. 
The archives preserve 47 documents of Byzantine date (1012-1447?), mostly of the 14th century, while the library contains around 187 manuscripts of the 15th century or earlier.