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. The smaller crater Weigel is located to the east.
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. There is no indication of a central peak. A low ridge runs to the north from the edge of the northern rim.
Segner lies within the southwest portion of the Schiller-Zucchius Basin.
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.