The Hynerian Empire is one of the major political entities on Farscape. A monarchy, the Hynerian Empire's head of state is a single, non-elected sovereign called a dominar. As of the first episode, it consists of 600 billion subjects. Hynerians are the dominant class.
The Rygel family has been in control for much of the Empire's history. However, 130 years before "Premiere," Rygel XVI was overthrown by his cousin Bishan (aided by the Peacekeepers) and sent into exile. Bishan's rule eventually became unfavorable, and by the time of "Lambs to the Slaughter," calls for his abdication spread to four of the Empire's primary home worlds. In spite of this, it isn't until the comic series that Rygel XVI reclaims the throne, albeit with force. During The War for the Uncharted Territories, the Hynerians were briefly conquered by the Kkore, and Rygel XVI's ex-wife Mmyna was installed as a puppet ruler.
The Hynerian Empire's influence spreads far across the Milky Way Galaxy. One planet, Acquara, was conquered thousands of years ago by the Hynerians before being forgotten about.
Farscape Roleplaying Game
2002's Farscape Roleplaying Game provides further detail into the history of the Hynerian Empire.
Over 10,000 years ago, the Hynerians left their homeworld for the first time. They perfected interstellar travel and began forging alliances with numerous planets, eventually forming the Cluster Republic. As the Hynerians increased their hold on these planets, outside forces attacked the Republic. The Hynerians declared martial law and used soldiers from the Republic's planets to defeat the enemy. At the end of the 42 year-long war, their aggressors were absorbed into the newly proclaimed Hynerian Empire. 9,000 years ago, Likan I became the first dominar.
Each planet within the Empire has representation in the Hynerian Member League, the Empire's legislative body. During emergencies, the dominar has the power to veto any decision made by the League.