Galen is a small lunar impact crater that lies in the rugged region between the Montes Apenninus range to the west and the Montes Haemus in the east.

It is located to the south-southeast of the crater Aratus, a slightly larger formation.

Galen is a circular crater with a bowl-shaped interior and a sharp rim that has not undergone significant erosion.

The small interior floor has a lower albedo than the surrounding walls.

The crater is named after ancient Greek doctor Claudius Galen.