Generation I of the Pokémon video games introduced 151 species. These original Pokémon are associated with Pokémon Red, Green, Blue, and Yellow and occupy National Pokédex numbers 001 through 151.
The first generation is set primarily in the Kanto region. Its best-known species include Bulbasaur, Charmander, Squirtle, Pikachu, Mewtwo, and Mew. The original games’ central goal of completing the Pokédex helped define Pokémon’s collecting-focused identity.
Mew is included in the total even though it was not normally obtained through standard gameplay in the original releases. Its existence became a famous secret and helped fuel interest in trading, rumors, and special distribution events.
The number 150 is a frequent near miss because Mewtwo is number 150, while Mew is number 151. Generation II later added 100 new species, bringing the cumulative total to 251 in the National Pokédex.