Sonnen is a small municipality located in the district of Passau within the state of Bavaria, Germany. Situated at an elevation ranging between 700 and 900 meters, the town is positioned in the vicinity of the Danube forest and the lower Bavarian forest.
The municipality lies approximately 28 km from Passau and 9 km from Hauzenberg. It is situated 13 km from the forest itself and borders upper Austria, which is located only 8 km away.