The Dionysiou Monastery (Greek: Διονυσίου) is one of the twenty monasteries located on the peninsula of Mount Athos in northeastern Greece. The monastery is on the southwestern side of the peninsula. Dionysiou ranks fifth in the hierarchical order on Mount Athos and is dedicated to St. John the Baptist.
Dionysiou Monastery was founded in the fourteenth century by St. Dionysios of Korysos. The golden bull (chyrsobull) authorizing the founding of the monastery was signed in 1374 by Alexios II Comnenos. A treasure, the bull is kept in the monastery. Construction proceeded with financial aid from emperor Alexios III Comnenos.
The monastery is built along the western coast of the peninsula on a rocky cliff high above the sea and overlooking a deep wooded ravine. In 1535, the monastery was swept by fire destroying it. Reconstruction began quickly and by 1547 the principal church of the monastery, the katholikon, had been built and painted with several murals (frescos) by the Cretan painter Tzortis. From these murals, the wall-paintings of Apocalypse are the oldest complete portrayal of the Apocalypse in the Orthodox world.
A golden iconostasis was added in the eighteenth century. Around the katholikon are a number of chapels including one that is dedicated to the Virgin Mary. Inside the monastery walls, a 25 meter high (80 feet) defensive tower was built in 1520. The tower was used periodically for safe keeping of the monastery’s library.
The relics of St. Niphon, Patriarch of Constantinople, one of the most well-known saints of Dionysiou are housed in a special crypt in the katholikon.