Which Pokémon game first introduced Pokémon Abilities to the main series?

Pokémon Ruby and Sapphire first introduced Pokémon Abilities to the main series.

Released for the Game Boy Advance in Japan in 2002, Ruby and Sapphire began the third generation of the core games. Abilities gave Pokémon additional passive effects that could influence battles or exploration.

Examples include Swampert’s Torrent, which strengthens Water-type moves when its health is low, and Zigzagoon’s Pickup, which can obtain items after battles. Abilities added strategic differences between species and, in some cases, between individual Pokémon.

Gold and Silver introduced held items, another major battle mechanic, but not Abilities. Hidden Abilities arrived much later, beginning with Pokémon Black and White’s special distribution and encounter systems.