Riemann (pronounced REE mahn) is a lunar impact crater that is located near the northeastern limb of the Moon, and can just be observed edge-on when libration effects bring it into sight.

It lies to the east-northeast of the large walled plain Gauss.

The outer rim has been worn away in many places, and now forms an irregular series of ridges in a rough circle.

The interior floor is a mixture of level terrain mixed with rough ground where impacts have stirred up the 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 Riemann.