Ansgarius is a lunar impact crater that is located near the eastern limb of the Moon. When viewed from the Earth, the crater has a highly oval shape due to foreshortening, but the rim is actually nearly circular. To the northwest of Ansgarius is La Pérouse crater, and south is the Behaim crater.

The rim of Ansgarius is not significantly worn, and has a terraced interior surface. The southwest rim appears somewhat flattened rather than round, and intrudes into an older formation of which little remains except the western rim. There is an outward notch in the north-northeastern wall. The interior floor of Ansgarius is relatively flat, with only tiny craterlets to mark the surface.

Satellite craters

By convention these features are identified on Lunar maps by placing the letter on the side of the crater mid-point that is closest to Ansgarius crater.