Reiner is a lunar impact crater on the Oceanus Procellarum, in the western part of the Moon. It has a nearly circular rim, but appears oval in shape due to foreshortening. The rim edge is well-defined and has not been eroded by impacts. In the midpoint of the irregular crater floor is a central peak. Outside the rim is a hummocky rampart that extends out across the mare for about half a crater diameter.