d'Alembert is a large lunar impact crater located in the northern hemisphere on the far side of the Moon, to the northeast of the somewhat smaller walled plain Campbell.

As with many lunar walled plains of comparable dimensions, the outer rim of this formation has been worn and battered by subsequent impacts.

As eroded as the rim may be, its form can still be readily discerned as a roughly circular ridge line in the lunar terrain.

A pair of shallow clefts in the floor surface radiate away from this crater, beginning near the midpoint of d'Alembert and reaching half-way toward the inner wall.

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