Around 1540, Metrophanes, the future patriarch of Constantinople  (1565-1572 and 1579 - 1580), re-founded the Holy Trinity monastery on the island of Chalki (currently Heybeliada, in the Sea of Marmara). In the following years he gradually endowed it with an important library. Formed of high quality volumes often of some antiquity, the Holy Trinity monastery library appears as one of the major collections of Greek manuscripts assembled in the former Byzantine capital then under Ottoman control.

In a fairly exceptional manner for a Greek library in the East, the history of the library can be reconstituted, particularly from several inventories, the oldest of which dates from patriarch Metrophanes’ time, from notes of possession indicated on the volumes themselves and from numerous references in travellers’ accounts.

 "Fathers, remember Metrophanes". Characteristic note of manuscripts of Holy Trinity monastery at Chalki.

The majority of the manuscripts are kept at the Holy Trinity collection (Hagia Trias) in the Library of the Oecumenical Patriarchate of Constantinople and are currently being catalogued by the IRHT team (A.Binggeli, M. Cassin, M. Cronier and M.Kouroupou).

Since 1844 the Chalki Theological School has been seated at the Holy Trinity monastery. If the manuscripts are no longer to be found there (they were transferred to the seat of the Patriarchate in the 1930s), the Theological School library today still houses a very fine collection of printed books.