- Founding Year: 2246 
- Capital (City, World): Dormuth, Marik
- National Symbol: purple eagle with spreaded wings
- Total (Inhabited) Systems: 24
- Government: Parliamentary Democracy (currently operating under military rule)
- Official Language: English (Czech and Slovak also common)
- Religion: Christianity (all kinds) and minorities (Judaism and Islam)
- Ruler: Captain-General Thomas Marik (3067)
As one of the founding states of the League it plays a central role in all important operation. It's the homeland of House Marik. On Atreus is the League's capital located and many important institution are also within its border. During its long history its suffer fewer casualties as other members of the league, because their central location at the heart of the state.
The Marik Commonwealth was founded by Charles Marik in 2246, as the successor to the Republic of Marik. When Republican forces captured Atreus as part of a campaign to expand the Republic by conquest, Charles moved his capital from the world of Marik to Atreus, reinventing the Republic as a new nation.
In 2265, the ruler of the Marik Commonwealth, Alonzo Marik, extended an offer to join the Commonwealth to the nations on the world of New Olympia; the three nations had been involved in numerous internal conflicts prior to this point, with the Terran Alliance having twice been forced to mount military interventions in the late twenty-second and early twenty-third centuries. Two of the nations on New Olympia, Kasnov and New Greenland, accepted Alonzo's offer; the third, Olympica, refused. The Marik Commonwealth then attempted to use military force to bring Olympica into the Commonwealth, but these efforts were stymied thanks to the intervention of the Regulan Principality. Olympica would ultimately be recognized as an independent principality by the Commonwealth, an independence it would continue to enjoy and exploit until at least the late thirty-first century.
Historical Maps (Gallery)
- Handbook: House Marik, p. 12
- Handbook: House Marik, p. 12, "To The Stars"
- House Marik (The Free Worlds League), p. 8-9, "Marik Origins"
- House Marik (The Free Worlds League), p. 154, "New Olympia"