The Terran Federation, founded in the late 21st century, is a federal republic, originally consisting of the nations of Earth, then, as humanity spread throughout the galaxy, its colony worlds. The Federation has seen several waves of expansion, most of them coinciding with or happening in the aftermath of interstellar conflict. There are three major political/astrographical blocs within the Federation: the Heart Worlds, consisting of the oldest and richest planets, including Terra itself; the Corporate Worlds, strategically-located systems dominated by major corporations and industrial combines; and the Fringe Worlds, the systems out in the frontier, which tend to be the last refuge for iconoclasts and peoples wishing to preserve their ethnic identities.
The Terran Federation is the largest and wealthiest power in the Starfire universe (as of the end of the 4th Interstellar War, 2370, in David Weber's The Shiva Option), a fact that garners mixed admiration and resentment among the other galactic powers. The Federation fought several wars with the Khanate of Orion during the 23rd century, until the events of the 3rd Interstellar War forced them to ally against the genocidal Rigellian hordes. Since then, the Federation and Khanate have had a mostly-friendly relationship, further solidified by the horrific experiences of the 4th Interstellar War in the late 24th century.