Poincaré is a large lunar impact basin that lies in the southern hemisphere on the far side of the Moon.

A rugged formation forms a low north–south range across the eastern section of the floor, possibly the remnant of an inner ring.

Directly to the west is Planck, a walled plain of similar dimensions to Poincaré.

Both formations are sufficiently large to have formed a small lunar mare on the near side face of the Moon.

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