Lunaria is the home world of the Moon Kingdom. It is also known as Luna IV, due to it being the fourth planet from the star it orbits, which is called Luna. Lunaria is home to just under four billion Lunarians spread across the globe, most of them living in the northern hemisphere of the planet.

The landmass of the planet is split up into several principalities, each of which is governed by one of the Great Houses of the Moon Kingdom, and they are known to rule with benevolence. As of the ascension to the throne of Neo-Queen Serenity, the Great Houses of the Lunarian home world were mostly headed by Sailor Scouts. The head of a Great House within the Moon Kingdom is known as a Princess, and upon death the title of Princess would pass on to a daughter. In the case of House Tsukino, upon death, the title of Princess [of the principality] and the title of Queen [of the Moon Kingdom] would pass to the daughter.

Lunaria has a diverse climate and ecosystem. There is plenty of snow and ice at the poles, plus it tends to get quite warm in the equatorial regions of the planet. The southern hemisphere is mostly one large ocean that encircles the planet, whereas in the northern hemisphere, there are mountain ranges, deserts, tundras, snow, meadows, forests, fields and more.