Martinsberg is a market town in the District of Zwettl, in the Austrian state of Lower Austria. It lies in the Waldviertel, the forested northwestern quarter of Lower Austria, a rural region of rolling hills and woodland.
As a market town (Marktgemeinde), Martinsberg holds a historic market right, a status that in Austria typically denotes a settlement of modest size that was granted the privilege to hold regular markets. It is one of the communities that make up the Zwettl district, whose administrative centre is the town of Zwettl.