Geminus is a lunar impact crater that is located near the northeast limb of the visible Moon. In this position the crater appears oval in shape due to foreshortening, but it is actually more nearly circular in form. Notable nearby craters include Messala to the northeast, Bernoulli due east, and Burckhardt and Cleomedes to the south.

Geminus of Rhodes was a Greek astronomer and mathematician. The dates of his birth and death are still under debate, but are generally accepted as approximately 110 - 40 BCE.