The Holy Monastery of Gregoriou is on the seashore and can be reached by the caique which brings visitors from Dafni, the port of the Athos peninsula. It was founded in the 14th century by the ascetic Gregorius, and is thus contemporary with the Monasteries of Dionysiou and Pantocrator. Little is known about the founder himself, other than that he was the disciple of the Blessed Gregorius of Sinai. The fires of 1500 and 1762, which destroyed the Monastery's archive, are undoubtedly in part to blame for this lack of information. However, even before the fires, the Monastery fell victim to the destructive mania of pirates. It recovered from the destruction of 1500 and was re-established with the help of Orthodox princes, among whom John Stephen the Great, Prince of Moldavia, played a leading role, and is for this reason regarded as a second founder of the Monastery.
Gregoriou succeeded in recovering from the disastrous results of the fire of 1762 through the efforts and qualities of leadership of Elder Ioakeim. He succeeded in collecting funds which made possible not only a new start for the Monastery, but also the redemption and freeing of captives. After his retirement, the Monastery adopted the idiorrhythmic system of monastic life. The resultant period of poverty through which the Monastery passed during the years of the Greek Revolution brought it to the point of seeking to become a dependency of the Monastery of the Megiste Lavra. We do not know the outcome of this request.
In 1840, it once again became a coenobium. In 1859 Symeon was appointed Abbot. During the 46 years for which he held office he paid off the debts of the Monastery, which amounted to 170,000 piastres, and gave support to the construction of new buildings. The new katholikon of Gregoriou was built in 1770 and its wall-painting was carried out in 1779. Its carved wooden sanctuary screen was also installed at that time. The second narthex was built in 1840 and the Chapel of St George in 1851. The katholikon is dedicated to St Nicholas. The Monastery possesses some 279 manuscripts, of which 11 are on parchment, and it has approximately 6,000 printed books. Among the Monastery's treasures are a small part of the True Cross, relics of saints, sacred vessels and vestments. The Monastery also has the miracle-working icon of Our Lady 'Palaiologina'. Gregoriou has seven chapels and six outlying chapels, while its dependencies consist of three kathismata and six kellia. Since 1574 it has held the seventeenth place in the hierarchy of the Athonite foundations. The brotherhood today consists of about 70 monks, of a high standard of education.