Eevee can evolve into eight different Pokémon species in the main series. These forms are Vaporeon, Jolteon, Flareon, Espeon, Umbreon, Leafeon, Glaceon, and Sylveon.
The first three evolutions appeared in the original games: Vaporeon, Jolteon, and Flareon. Pokémon Gold and Silver added the friendship-based Espeon and Umbreon, while later generations introduced Leafeon, Glaceon, and Sylveon through different evolution conditions.
Eevee is unusual because its branching evolution family is a central part of its identity. The games use different methods, including elemental stones, friendship with a time-of-day condition, location-based mechanics, and knowledge of a Fairy-type move.
Eevee is not itself a collection of eight forms; it is one species with multiple possible evolutions. Regional forms and special partner versions can create additional visual distinctions, but they do not increase the standard count of eight species.