(Μονή Κοσταμονίτου) is an orthodox christian monastery
at the monastic state of Mount Athos
. It stands on the south-eastern side of the Athos peninsula. The monastery ranks twentieth in the hierarchy of the athonite monasteries.
The monastery was founded in 11th century. It is dedicated for Saint Stephen.
The monastery has about working 20 monks.
The library of monastery holds 110 manuscripts and approximately 5,000 printed books.