"Bandit kingdom" is a label applied to small Periphery powers that share certain characteristics. A typical bandit kingdom holds sway over one or more star systems located near the Inner Sphere's outer rim, is ruled by some form of despot, and subsists primarily through piracy and raiding its neighbors.
Raiders preying upon vulnerable Periphery and Inner Sphere worlds were a recurring feature of the galactic scene since at least the Reunification War, and two bandit kingdoms, the Tortuga Dominions and Circinus Federation, were both in existence by the time the Star League was dissolved. It was not until the Succession Wars, however, that bandit kingdoms arose in numbers. Between the fall of the Star League, the collapse of the Rim Worlds Republic, and all-out warfare between the Great Houses, pirates, ex-mercenaries and military deserters were able to establish permanent settlements near their raiding targets.
Over time a number of these pirate havens grew into organized states, albeit ones that were ruled by petty monarchs and had only a semblance of proper government apparatus. Nonetheless, by the 31st century the more powerful of these bandit kingdoms, such as the Oberon Confederation and Marian Hegemony, had acquired enough respectability to be treated as legitimate states by the Inner Sphere powers.
The latter half of the 31st century saw a radical shift in the political landscape of the bandit kingdoms. The Clan Invasion led to the sudden destruction of the Oberon Confederation and its neighbors, while the Marian Hegemony conquered the Illyrian Palatinate and Lothian League and came to be seen as the Periphery's fourth major nation rather than a 'mere' bandit kingdom. The Jihad ended with the dissolution of the Circinus Federation when its capital was razed by Regulan forces, while new bandit kingdoms such as the Rim Territories and those of the Barrens, arose from marginal worlds abandoned by the Lyran Commonwealth and Clan Hell's Horses.  
List of Bandit Kingdoms
- Barony of Strang (2775 - 3049)
- Circinus Federation (2785 - 3081)
- Greater Valkyrate (3021 – 3049)
- Marian Hegemony (2920 – present, not considered a bandit kingdom by c. 3050)
- Oberon Confederation (2775 - present, nonexistent or Clan-occupied at various times)
- Rim Territories (3087 - present)
- Santander's World (3019 - 3049)
- Tortuga Dominions (late 2500s - present)
Essex's World is listed among the Bandit Kingdoms in The Periphery First Edition but not The Periphery, 2nd Edition. Given the "Secondary Source" status attributed to First Edition (see that book's Canonicity section for details), the current status is unknown.
- The Periphery, 2nd Edition, p. 79
- The Periphery, p. 143-154
- The Periphery, 2nd Edition, p. 54
- Dark Age: Touring the Stars, p. 95-96
- The Periphery, First Edition, p. 62 "THE BANDIT KINGDOMS"