Generation III introduced 135 new Pokémon.
The generation began with Pokémon Ruby and Sapphire for the Game Boy Advance in 2002. These games introduced the Hoenn region and expanded the Pokédex from the earlier 251 species to 386.
Generation III also included Pokémon Emerald, an enhanced version of Ruby and Sapphire, followed by the Game Boy Advance remakes Pokémon FireRed and LeafGreen. The remakes returned players to Kanto but did not add a new generation of species.
The figure 135 refers to new species introduced in Generation III, not the total number of Pokémon available in those games. That distinction causes frequent confusion: the generation’s regional additions number 135, while the cumulative Pokédex total reached 386. Generation IV later added 107 more species.