As of October 2402, there were 155 member states of the United Federation of Planets, and Federation space spanned over 10,000 light-years. (ST novel: Articles of the Federation)

On new stardate γ 2143.21.3, the Federation celebrated the induction of all remaining space-faring civilizations of the Milky Way Galaxy. (ST novel: Federation)

By the year 1,012,260, the Mega-Federation controlled the entire galaxy, and was able to move it through intergalactic space at will. (ST - Strange New Worlds VI short story: "Our Million-Year Mission")

See also Federation colonies.

Founding member states[]

The United Federation of Planets was founded in 2161 by the governments of United Earth, the Confederacy of Vulcan, the Andorian Empire, the United Planets of Tellar, and the Alpha Centauri Concordium, all of which were previously members of the Coalition of Planets. (TNG episode: "The Outcast"; ENT episode: "Zero Hour"; ST novel: Articles of the Federation; ENT novel: Kobayashi Maru; ST reference: Star Fleet Technical Manual)

The novel Starfleet: Year One, published before Enterprise canonically confirmed the founding members of the Federation, gave eight founding worlds; Earth, Vulcan, Andor and Tellar remained, Alpha Centauri was omitted and Osadj, Dedderai, Vobilin and, last to agree to join, Rigel IV, were added. While these extra worlds could still be early members of the Federation, the majority of sources, and canon, now rule them out as founding members.

Similarly, the reference book Spaceflight Chronology lists Rigel as a founding member in addition to the five listed above. In addition, in that source Alpha Centauri is a system with an indigenous (though closely related to Human) population, not an Earth colony.

Members[]

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Withdrawal from the Federation[]

Member worlds, colonies and species have occasionally left the Federation, or had their membership withdrawn.

In 2165, the Orion Syndicate manipulated public opinion on Vulcan to force them into a secession. The plan was foiled by Starfleet. (ENT - Rise of the Federation novel: Uncertain Logic)

Between the 23rd century and the 2370s, the Caitians withdrew and reapplied for Federation membership repeatedly. Cait was welcomed back each time. (NF - Gateways novel: Cold Wars)

In 2376, the revelation of manipulation in the Federation Council by the Selelvians left to the membership of their homeworld Selelvia to be revoked. This led to the Selelvian War between the Federation, the Selelvians, and their Tholian Assembly allies. (NF novel: Stone and Anvil)

In 2378, a Changeling manipulated the government of Kerovi into withdrawing from the Federation. (VOY - Spirit Walk novel: Enemy of My Enemy) Despite the revelation of foreign intervention, the Kerovian leader stuck to the decision to save face. (VOY novel: Full Circle)

Following the reallocation of refugees and resources in the wake of the Borg Invasion of 2381, several worlds threatened plebiscites on maintaining their Federation membership, chiefly Alpha Centauri IV. Following an eye-opening experience for the leader of the Alpha Centauri Concordium of Planets, the votes instead became reaffirmations of their membership. (TNG novel: Losing the Peace)

In 2382, the Andorian Empire voted to secede from the Federation. Relations were frosty and an alliance between Andoria and the hostile Typhon Pact was deemed possible. (Typhon Pact novel: Paths of Disharmony) The Andorians rejoined in 2385. (ST - The Fall novels: A Ceremony of Losses, Peaceable Kingdoms)

The re-dedication of Starfleet to undertake the evacuation of the Romulans led to 14 planets threatening withdrawal in the 2380s decade. The issue became moot in 2385 when the Wallenberg-class rescue fleet was destroyed by Synths. (PIC novel: The Last Best Hope)

Continued support for reconstruction in the Cardassian Union and Romulan successor states led to Pacifica withdrawing in protest in the 2390s. The Pacificans were unwilling to subsidize "enemies of the Federation". (STO reference: The Path to 2409)

Following a galactic cataclysm in the 3060s<ref>DSC episode: "Die Trying", the Burn, the Federation largely collapsed as a power. (DSC episode: "That Hope Is You, Part 1")

Starfleet Headquarters and Federation Headquarters left Earth soon after, and United Earth pulled out of the Federation. (DSC episode: "People of Earth") Trill also dropped out. By 3189, the Trill awaited the return of the Federation. (DSC episode: "Forget Me Not")

At that time, practised Federation membership had reduced from 350 to 38 planets. (DSC episode: "Die Trying")

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