Inner Sphere

In the BattleTech universe, the Inner Sphere is a region of interstellar space, ruled by the five Great Houses (each of which dominates one of the "Successor States".) After the fall of the mediating Star League, the Great Houses turned on each other as each attempted to succeed to the throne of the Star League in what became known as the Succession Wars.

The Inner Sphere is surrounded by the Periphery. The Inner Sphere perceives the relationship between these regions as analogous to that of the developed nations and the Third World, though some of the major Periphery nations compare well with the weaker Houses.

Beyond the Periphery is unexplored space (sometimes called the Deep Periphery). The Clans exist in a small islet of settled worlds in the Deep Periphery.