The Aschau is a stream in the Südheide Nature Park in Lower Saxony, Germany, It is a tributary of the Lachte, which in turn discharges into the Aller.

The area is also a habitat for gudgeon, roach, stickleback, bitterling and swan mussels.

It passes under the B 191 federal road, is joined from the left by the Postmoorgraben, and then flows through extensively managed meadows and natural, original forest to Eschede, before continuing to Habighorst.

It then picks up the Quarmbach from the right, a stream which rises in Rahmoor, and which forms a large swamp and lake area just before its confluence with the Aschau.

[3] By the 15th century the Quarmbach had been impounded to drive the local mill, the Quarmühle and some of the ponds must date back to that period.