The first generation of the main Pokémon video games introduced 151 Pokémon species.
These creatures appear in Pokémon Red, Green, Blue, and Yellow, which make up the first generation of the core series. The National Pokédex order runs from Bulbasaur, number 001, to Mew, number 151. Mew is included even though it was a mythical Pokémon distributed through special events rather than normally encountered during the original story.
The original games’ goal of completing the Pokédex helped define Pokémon’s identity. Version exclusives encouraged players to trade, while evolution created additional ways to obtain species. The 151 number is therefore connected not only to the games’ content but also to the social design of the link-cable system.
The first generation is sometimes described as containing 150 Pokémon because Mew was difficult to obtain officially. However, the complete original Pokédex included 151 species. Later generations expanded the total substantially, but the original 151 remain the foundation of the franchise’s earliest era.