The Royal Government is the ruling system over the people of Eldia on Paradis Island. From the royal capital Mitras, the false Fritz family had for the past hundred years acted as the face of the royal government while the Reiss family, formerly the true Fritz family, acted as the secret ruling bloodline. After the coup d'état, a majority of the old government was displaced in favor of a military-led system with the Reiss family ruling publicly. Historia Reiss is currently in command as Queen of the Walls. In 854, the militant ultranationalist Jaegerists took power within the Walls and kept a similar system in a post-Rumbling Eldia.
History: During the reign of Uri Reiss, one of the members of the council informed Kenny Ackermann of the Reiss family's true lineage. Rod Reiss and Uri realized that they needed to root out the identity of the informant. After Kenny's attempt to assassinate Uri failed, this member was removed from his position and Kenny was rewarded with his place at the council.
Story: In 846, the royal government decided to abandon the territory within Wall Maria, one year after its fall. After the operation where Eren Jaeger was rescued from Reiner Braun and Bertholdt Hoover, the Assembly summons Erwin Smith to the chancellery in Mitras. During his meeting with the Assembly, Erwin concludes that the nobility within the Royal Government cares only for their own positions and possessions, giving no regard to humanity as a whole.
Source: Royal Government (Anime), available under CC BY-SA 3.0.