MacMillan is a bowl-shaped lunar impact crater

Impact crater

In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...

 on the eastern fringes of the Mare Imbrium

Mare Imbrium

Mare Imbrium, Latin for "Sea of Showers" or "Sea of Rains", is a vast lunar mare filling a basin on Earth's Moon and one of the larger craters in the Solar System. Mare Imbrium was created when lava flooded the giant crater formed when a very large object hit the Moon long ago...

. It is located just to the southwest of a lone rise, near the southwestern edge of the Montes Archimedes

Montes Archimedes

Montes Archimedes is a mountain range on the Moon. It is named after the crater Archimedes that lies to the north, which in turn has an eponym of the Greek mathematician Archimedes....

. This is a cup-shaped depression in the surface with an interior albedo

Albedo

Albedo , or reflection coefficient, is the diffuse reflectivity or reflecting power of a surface. It is defined as the ratio of reflected radiation from the surface to incident radiation upon it...

 that matches the nearby lunar mare

Lunar mare

The lunar maria are large, dark, basaltic plains on Earth's Moon, formed by ancient volcanic eruptions. They were dubbed maria, Latin for "seas", by early astronomers who mistook them for actual seas. They are less reflective than the "highlands" as a result of their iron-rich compositions, and...

. The edges of the rim have a somewhat higher albedo.

This crater was previously identified as Archimedes F before being named by the IAU

International Astronomical Union

The International Astronomical Union IAU is a collection of professional astronomers, at the Ph.D. level and beyond, active in professional research and education in astronomy...

.