The United Planets is the dominant government of the known universe in the current Year 21,888.  It covers tens of millions of light years and over 1000 galaxies.  It's capital is Alfheim, and it was preceeded by the Star Imperium.  It was founded in Year 13,100. 

It's central government is composed of the Council of Twelve, the United Planets Assembly, the Prime Minister, and the Council of Ministers.