Pokémon X and Y introduced the Fairy type to the main series.
Released worldwide for the Nintendo 3DS on October 12, 2013, Pokémon X and Y added Fairy as the series’ eighteenth type. It was the first new type introduced since the Dark and Steel types appeared in Pokémon Gold and Silver in 1999.
The new type changed battle matchups and gave several existing Pokémon new classifications. For example, older Pokémon such as Clefairy and Marill gained the Fairy type, while new Pokémon such as Xerneas were designed around it.
Fairy-type Pokémon are especially associated with effectiveness against Dragon-type Pokémon, helping rebalance a matchup that had been unusually dominant in earlier generations. The type is sometimes confused with the games’ new Mega Evolution mechanic, but Fairy and Mega Evolution were separate additions introduced in the same generation.