The third generation introduced 135 new Pokémon.
These species debuted with Pokémon Ruby and Sapphire, released for the Game Boy Advance in 2002. They brought the National Pokédex total to 386 and introduced the Hoenn region, a setting built around islands, sea routes, volcanic terrain, and tropical environments.
The generation added several major gameplay features, including Pokémon abilities, natures, double battles, contests, and customizable Secret Bases. Treecko, Torchic, and Mudkip formed the starter trio, while the new Legendary Pokémon included Groudon, Kyogre, and Rayquaza.
The number 135 describes the species added across the generation, beginning with Treecko and ending with Deoxys in National Pokédex order. Pokémon Ruby and Sapphire themselves did not allow players to catch every existing species, so the generation’s total should not be confused with the number available in one cartridge.