New Iridia (Iridia IV) is a terrestrial planet in the Iridia system. Colonized after Iridia III, it lacks the phenomenal native metal resources of the other planet, but was markedly more hospitable, able to support Terran plant life. (And not having at atmosphere full of poisonous metal carbonyls.) Thanks to this plant life, the atmosphere now contains molecular oxygen, though not yet in concentrations sufficient to directly sustain human life. Habitats are provided with oxygen concentrators and carbon dioxide scrubbers to make the atmosphere breathable. When the Empire fell, the infrastructure to create the molecular sieves needed for oxygen concentrators was lost, and a population contraction occurred. Survivors made do with the limited stock of precious molecular sieves, oxygen obtained by chemical reactions and electrolysis, and abundant green plants. New Iridians are to this day said to be inordinately fond of vegetation in their homes and working environments.

In time, New Iridia recovered technologically and industrially, and recolonized Iridia III, the population of which had died out during the Collapse. The capital of the Allied Worlds is a space station orbiting New Iridia.