Alliance of Unified Planets
Ubiquitously known as the Alliance, this is the dominant ruling faction of the Galaxy. The Alliance boasts memberships of thousands of worlds across the galaxy. Unfortunately for the Alliance, it's size makes it a slow unwieldy beast to bring to bear against threats. With the rise of the Empire, and their pledge to bring peace to the galaxy (something the Alliance has struggled to do) many have begun to fear that the alliance has grown too long in the tooth to maintain power across it's breath-takingly vast territory.
Members
Members of the Alliance come in every shape, size, color, and origin imaginable. The alliance stretches across thousands of worlds and as soon as a planet's application to the Alliance is approved, all of it's population is granted citizenship with all the rights and responsibilities therein. Practically speaking, this means very little to day to day life on member worlds.
The local security forces are drafted under the umbrella of Alliance Security, often with little benefit except the basic tools needed to meet the lowest galactic standards. Alliance Security officials are required to do an inspection of membership worlds and there security forces every three galactic standard years. The problem is with so many worlds inspectors are hard pressed to do a thorough inspection of every world on this limited time table. Many local governments have learned that a relatively small amount of credits in respect for an inspector's busy schedule can often result is a rubber stamp of approval without too much fuss. This often leads to the local security forces being little more than unregulated, jackbooted thugs serving the whims of the local magistrates.
Worlds
Base World: Tau Felis Prime (K10)
Notable Worlds: Many
Any questionably civilized planet can apply for entry into the Alliance and as long as these worlds pay their taxes and pledge any ships under their control to the defense of the Alliance, they get to benefit from the Alliance's vast reach. Standardized currency and Market stabilization are the two largest draws of Alliance membership, as well as being considered a trade partner in good standing, ensuring licensed alliance vessels make regular trips to each planet to trade. It also means access to the Alliance Cortex network, allowing communication between Alliance worlds and ships built on those worlds (that is to say virtually EVERY ship in the verse) almost instantly. However, this also means that individuals or ships flagged as wanted on one Alliance world, are flagged on ALL alliance worlds almost immediately.
Ships
The Alliance has the largest fleet in the Galaxy. That is of course assuming that every single alliance world honors it's responsibilities and makes them available when the Alliance calls on them. In addition, the Alliance reserves the right to "draft" independently owned and operated vessels into their navy at any time. Typically the owner and crews of said ship are dully compensated for their assistance with whatever issue needed to be dealt with.