Sonntagberg is a town in the district of Amstetten, in the state of Lower Austria, Austria. It lies in the eastern part of the country, within the Amstetten district of the Mostviertel region.
The town is an important pilgrimage destination for Catholics. Its basilica church is frequently cited as one of the most beautiful buildings in the area, and the pilgrimage tradition is the feature for which Sonntagberg is best known.