Liebig is a lunar crater that is located to the south-southeast of the crater Mersenius, and west of the Mare Humorum in the southwest part of the Moon. To the southwest of Liebig is the slightly smaller crater de Gasparis.
The rim of Liebig has a low inner wall, with an interior floor that is nearly featureless except for a few tiny craterlets. It is nearly, but not quite circular, with outward bulges to the west and southeast. The small, cup-shaped crater Liebig A lies along the inner wall and part of the interior floor.
The western edge of the Mare Humorum is a fault line designated the Rupes Liebig, named after this crater. This fault extends for about 180 km along the shore. To the southwest, in the section of lava-flooded surface between Liebig and de Gasparis, is a system of rilles named the Rimae de Gasparis. These cover an area with a diameter of 130 km.