The politics within the Star Imperium and later the United Planets saw the Imperial Parliament, United Planets Assembly, and the assemblies of the Stellar sectors and Subsectors divided into a number of factions.

Under the Star Imperium, there was the Monarchist Party, itself divided into Blue Monarchists, Red Monarchists, and the Moderate Party; and the Freethinkers, a pro-republic faction that wanted to abolish the monarchy of the Imperial Sovereigns.

After Year 13,100, the main parties in the United Planets were the Freethinkers, the Monotheist Party, and the Incarnate Party.