Segner is a lunar impact crater located near the southwestern limb of the Moon, to the northeast of the giant walled plain Bailly.

The crater Zucchius is a few kilometers to the south-southwest of the rim, and to the north east lies the unusual formation Schiller.

Segner has a low, worn rim, and is generally much less prominent than the nearby Zucchius.

The floor is distinguished only by a pair of small craterlets and a slightly undulating surface.

By convention these features are identified on lunar maps by placing the letter on the side of the crater midpoint that is closest to Segner.