Guillaume is an old lunar impact crater on the Moon's northern hemisphere, and is located on the far side relative to the Earth.

This is a worn and eroded formation, with features that have been softened and rounded over time.

The bowl-like interior is nearly featureless, with only a few small craterlets to mark the surface.

Prior to formal naming by the IAU in 1979,[1] Guillaume was called Crater 73.

[2] By convention, these features are identified on lunar maps by placing the letter on the side of the crater midpoint that is closest to Guillaume.