Posterholt (in Limburgs Postert) is a church village in the municipality of Roerdalen, with more than 4000 inhabitants it is the largest place in the municipality. Posterholt was also an independent municipality until 1991. For the French period, Posterholt together with the neighboring village of Vlodrop formed a ship bench.
Posterholt is located near the border with Germany, which runs east of the place. On the other side of Posterholt lies quite extensive forest area. The area of the village is alternately rural (agricultural) and woodland. The monumental castle of Aerwinkel is located in the surrounding forests. The forests, mainly consisting of coniferous trees, have grown on sandy soils that are sputtered into dunes. There is a lot of relief in this area, with altitude differences up to 20 meters. In addition, the agricultural areas include the Holster, Vlodropper and Voorsterveld fields around the village. Along the village, the Leigraaf and, more south, flow the Vlootbeek, which flows directly across the German border and opens at Linne in the Meuse.
Central in Posterholt, but also on the outskirts, is a Roman Catholic church of the H. Matthias parish. The classical Sint-Matthias church has been here since 1951, after the Germans damaged the earlier church from 1878 during the war that it could no longer be restored. The old St. Matthew church stood in a different location in the village, more southeast than now. The street name Kerksteeg still reminds us of this.