Nunn is a lunar impact crater that is located just beyond the eastern limb of the Moon, along the northern edge of Mare Smythii. It was named after American engineer Joseph Nunn.^[1] To the east of this crater is the much larger Babcock, and to the northwest is Jansky.

This is a circular, bowl-shaped crater with some impact wear along the northwestern rim and to a lesser degree along the southeastern edge. The remainder of the crater perimeter is relatively free of erosion, and the edge is well-defined. The darker-hued interior floor is about half the crater diameter, and is level and almost featureless.