Wallach is a tiny lunar impact crater located in the eastern Mare Tranquillitatis.

It was named after German chemist and Nobel laureate Otto Wallach in 1979.

[1] It is a circular, bowl-shaped feature with a negligible interior floor; the inner walls just slope down to the midpoint of the crater.

Wallach is located to the northeast of the crater Maskelyne, near some low ridges in the lunar mare.

[2] The feature was photographed repeatedly from its emergence on the horizon to after the Command Module had passed directly over it.