In the fictional 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 Star League, the Inner Sphere fractured as each of these Houses attempted to secure rulership during the Succession Wars. The Inner Sphere is bounded by the Periphery; the relationship between these regions is analogous to that of the developed nations and the Third World. Beyond the Periphery is unexplored space, and the Clans.

Worlds of Note

Capitals

New Avalon

Capital of both the Federated Suns and the Federated Commonwealth.

Luthien

Capital of the Draconis Combine.

Sian

Capital of the Cappellan Confederation.

Atreus

Capital of the Free Worlds League.

Tharkad

Capital of both the Lyran Alliance and the Federated Commonwealth

Solaris VII

Located in Lyran space, Solaris VII is also known as the gaming world.