Insignia of the Alpha Centauri Concordium of Planets
The Alpha Centauri Concordium of Planets (often shortened to Alpha Centauri Concordium or simply Centauri Concord) was an interplanetary alliance and government of worlds in the Alpha Centauri system, including planets orbiting all three stars, Alpha Centauri A, Alpha Centauri B and Alpha Centauri C (Proxima).
The Concordium was founded in the early 21st century by the two races that inhabited Alpha Centauri IV and Alpha Centauri VII, and their colonies within the system. The practical experiences they gained through their early efforts at colonization and the cooperation that fostered between the two worlds led them to join in the first representative interstellar government. This political confederation eventually served as one of the models on which the United Federation of Planets was based. (FASA: The Federation)
The native worlds of the Concordium welcomed the human colonies on Centauri B II, Proxima II and Alpha Centauri III with open arms, and the worlds shared trade and friendship for many years, eventually reaching the point where native-born Centauri and the Earth colonists were so integrated they viewed themselves as one grand culture. When those colonies eventually declared their independence from the United Earth, they were offered admittance into the Concord should they so choose, and by the 2150s, all of the planets within the system were fully recognized as members of the Concordium.
The Concordium joined with the United Earth, Confederacy of Vulcan, United Planets of Tellar and Andorian Empire to form the Coalition of Planets in 2155, and continued in that alliance throughout the period of the Earth-Romulan War. In 2161, those five entities together founded the United Federation of Planets as a more permanent interstellar union. (Star Fleet Technical Manual; Worlds of the Federation; ENT novel: A Choice of Futures, The Good That Men Do; ST novel: Articles of the Federation)