Mare Humboldtianum

thumb|right|260px|Elevation map of Humboldtianum basin

thumb|right|260px|Oblique view from [[Apollo 16]]

Mare Humboldtianum (Latin humboldtiānum, the "Sea of Alexander von Humboldt") is a lunar mare located just to the east of Mare Frigoris, in the center of Humboldtianum basin. It is located along the northeastern limb of the Moon, and continues on to the far side. Due to its location, the visibility of this feature can be affected by libration, and on occasion it can be hidden from view from Earth.

The basin material is of the Nectarian epoch,

This mare is situated between near (visible) and far sides of the Moon, like a link between known and unknown. That's why Johann Mädler named it after Alexander von Humboldt, a prominent explorer of unknown lands.