A loose political and paramilitary network representing the interests of Belters - the inhabitants of the asteroid belt and the moons of the outer planets. Founded in opposition to inner planet exploitation of Belt labour and resources, the OPA ranges from legitimate advocacy to violent resistance depending on its faction and leadership.

The governing body established to manage transit through the ring gates and coordinate shipping across the thirteen hundred new colony systems. Successor to the OPA's political role, the Transport Union holds enormous economic power over the gate network.