Bilharz is a lunar impact crater that lies in the eastern part of the Mare Fecunditatis. It is the largest member of a close triple-crater formation with Atwood to the east and Naonobu to the northeast. To the southeast is the prominent crater Langrenus.
The interior of this crater has been resurfaced by basaltic lava, leaving the floor flat, shallow, and nearly featureless. There is no central peak at the midpoint, and little to mark the interior except for a few tiny craterlets. The outer rim remains circular and only slightly worn.
Prior to being named by the IAU in 1976, this crater was identified as Langrenus F, a satellite crater of Langrenus.