Byrgius is a lunar impact crater located in the western part of the Moon, near the limb.

As a result, Byrgius appears strongly oval in shape due to foreshortening.

The floor is relatively flat and undistinguished by significant craters.

Byrgius A possesses its own ray system that extends for over 400 kilometres.

By convention these features are identified on lunar maps by placing the letter on the side of the crater midpoint that is closest to Byrgius.