The Mosbrucher Weiher, also called the Mosbrucher Maar, is a silted up maar east of the municipal boundary of the village of Mosbruch in the county Vulkaneifel in Germany. It is located immediately at the foot of the 675-metre-high Hochkelberg, a former volcano. The floor of the maar is in the shape of an elongated oval and is about 700×500 metres in size, its upper boundary has a diameter of about 1,300 × 1,050 metres. This makes the Mosbrucher Maar the third largest of the maars in the western Eifel region. The Üßbach stream flows past and close to the Mosbrucher Weiher.