The Holy Monastery of Konstamonitou stands in one of the most picturesque spots on Athos, surrounded by woodland and half an hour away from the Singitic Gulf. A tradition makes the founder of the Monastery Constantine the Great or one of his sons, but it is more likely that its foundation is connected with an ascetic of the name of Kastomonites, hence the Monastery's alternative name of Kastamonitou. There are references in certain texts of the 11th century to Kastamonitou, but its history can be clearly traced only from the 14th century onwards - a period at which the Monastery suffered badly from pirate raids.
Among the Monastery's benefactors were Prince George Brancovits, Anna, Princess of Serbia, and Radits, Commander-in-Chief of Serbia, who helped the Monastery in a variety of ways in the 15th century. However, in spite of such financial support, the taxation of the Turks led the monks to obtain loans from Jewish moneylenders and brought the Monastery close to ruin. In 1705, the intervention of the French Consul Armand was the salvation of Konstamonitou. In 1717 the east wing of the Monastery was burnt down. Restoration began in 1818 under Abbot Chrysanthos with help from Kyra Vassiliki, the wife of Ali Pasha (of Yannina). In the mid 19th century the poor financial state of the Monastery led to its being put under the guardianship of the Holy Community. The vigorous Abbot Symeon helped to put the Monastery on its feet again and with the funds which he amassed built the katholikon in 1867 on the ruins of its predecessor, and restored other buildings. The katholikon is dedicated to St Stephen the Protomartyr.
The Monastery has five chapels within its precinct and four outside. Among its treasures are a miraculous icon of St Stephen, a work of the 8th century, and two wonder-working icons of Our Lady Hodeghetria and Our Lady Antiphonetria. It also possesses a piece of the True Cross, a Byzantine liturgical bier cover, vestments, and sacred vessels. The library of Konstamonitou contains 110 manuscripts and approximately 5,000 printed books. The Monastery occupies twentieth place in the hierarchy of the monasteries and today has some 30 hardworking monks.