Osiou Grigoriou (Gregory's) monastery (Greek: Μονή Οσίου Γρηγορίου) is an Orthodox Christian monastery in the monastic state of Mount Athos in Greece. The monastery ranks seventeenth in the hierarchy of the Athonite monasteries.
The monastery is built by the sea, on the southeastern side of the peninsula.
The monastery is dedicated to Saint Nicholas.
In 1990 the monastery had 71 working monks.
The Monastery holds 279 manuscripts, of which 11 are on parchment, and it has approximately 6,000 printed books.