Eeveelution is a term used for the current group of eight Pokémon that evolve from Eevee. It is a portmanteau of the words "Eevee" and "evolution". Its definition may be extended to include Eevee itself.
Generation I[]
In Generation I, only one Eevee is obtainable in-game, at the Celadon Mansion. It can evolve into Vaporeon, Jolteon, or Flareon through the use of an Evolution stone.
 Eevee |
 Vaporeon |
 Jolteon |
 Flareon |
Generation II[]
Eevee is available relatively early in Pokémon Gold, Silver, and Crystal, but keeps its rarity. Generation II introduced friendship and a day-night cycle, and alongside them, two new Eeveelutions that take advantage of the new mechanics: Espeon and Umbreon. Each of Ecruteak City's Kimono Girls owns one of the five Eeveelutions that existed in Generation II.
Eevee cannot evolve into Espeon or Umbreon in Pokémon FireRed and LeafGreen, due to the absence of a day-night cycle. However, as both are present in the games, they can be legitimately obtained in a save file by trading an Eevee to Pokémon Ruby, Sapphire, and Emerald, evolving it there, and then trading back, or by trading from Pokémon Colosseum or Pokémon XD: Gale of Darkness.
 Espeon |
 Umbreon |
Generation IV[]
After an entire generation with no new Eeveelutions, Generation IV added another pair of Eeveelutions, Leafeon and Glaceon, which are obtained by leveling Eevee up in certain areas—another departure from the methods of evolution in previous generations. Since Generation VIII, however, they can also be obtained through the use of an Evolution stone.
Eevee cannot evolve into Leafeon or Glaceon in Pokémon HeartGold and SoulSilver, due to the absence of the areas required for its evolution in either of the regions the games are set in. However, as both are present in the games, they can be legitimately obtained in a save file by trading in from Pokémon Diamond, Pearl, and Platinum.
 Leafeon |
 Glaceon |
Generation VI[]
Once again, an entire generation passes by before the introduction of a new Eeveelution in Generation VI: Sylveon. Its reveal also introduced the Fairy-type to the public.
 Sylveon |