The Royal Government is the ruling system over the people of Paradis Island. From the capital of Mitras, the false Fritz monarchy 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.
History: It is said that the Royal Government held significance over humanity even before the Titans first appeared; the royal bloodline having been unbroken for as many as 2,000 years. During the reign of Uri Reiss, one of the noblemen of the Assembly informed Kenny Ackerman of the Reiss family's true royalty. After Kenny's attempt to assassinate Uri failed, this nobleman was removed from the Assembly and Kenny took his place.
Story: After the operation where Eren Yeager was rescued from Reiner Braun and Bertolt 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. Conspiring with Dot Pixis, together they plan to overthrow the monarchy and appoint a new leader who will work towards the betterment of humanity and allow the Survey Corps to continue its attempts to reach Shiganshina District.
Source: Royal Government, available under CC BY-SA 3.0.