Eevee has the greatest number of official evolutions among Pokémon species, with eight.
Its current evolutions are Vaporeon, Jolteon, Flareon, Espeon, Umbreon, Leafeon, Glaceon, and Sylveon. Fans often call this branching family the Eeveelutions. Unlike a standard linear evolution chain, Eevee can develop into different forms depending on an item, location, friendship, time, or move-related condition.
Eevee debuted in the first-generation games, where it could evolve into Vaporeon, Jolteon, or Flareon using Water, Thunder, or Fire Stones. Later generations added the remaining forms, with Sylveon completing the current set in Generation VI.
Eevee’s number of evolutions can change only if a future Pokémon generation adds another official form. Regional forms and temporary transformations are not automatically counted as separate Eeveelutions. The answer therefore refers to named species that Eevee can evolve into, not every alternate appearance or battle form.