Which Pokémon games first introduced Pokémon Abilities?

Pokémon Ruby and Sapphire first introduced Pokémon Abilities.

Released for the Game Boy Advance in Japan in 2002, Ruby and Sapphire were the first main-series games to give Pokémon passive Abilities. These traits can affect battles or exploration without being selected as ordinary moves. For example, some Abilities alter damage, protect a Pokémon from particular effects, or influence encounters.

Abilities added another layer of strategy because two Pokémon of the same species could differ in the trait they possessed. This made species choice more nuanced and encouraged players to consider team combinations, not just move power and type matchups.

Gold and Silver introduced held items and other battle innovations, but they did not introduce the Ability system. Abilities have remained a core mechanic in later generations, although individual effects and the number of available Abilities have changed. Ruby and Sapphire also introduced the Hoenn region, double battles, Pokémon Contests, and natures.