Pokémon Ruby and Sapphire introduced 135 new Pokémon species.
The games formed the core of Pokémon’s third generation and expanded the Pokédex substantially beyond the 251 species available after Gold and Silver. The new species included Treecko, Torchic, Mudkip, Gardevoir, Absol, Rayquaza, and many others.
Ruby and Sapphire were released for the Game Boy Advance in Japan in 2002 and internationally in 2003. Alongside the new species, they added abilities, natures, double battles, Pokémon Contests, and a new region called Hoenn.
The number can be confused with the 100 species introduced by Gold and Silver or the 156 species introduced by Black and White. The 135 figure refers to species first introduced in the original Ruby and Sapphire generation, not the total number available in the games.