The original Pokédex included 151 Pokémon.
Pokémon Red and Green introduced the first generation of species, numbered from Bulbasaur at 001 to Mew at 151. Players could encounter most species during normal play, while version exclusives and evolutions encouraged trading between cartridges.
The number is sometimes given as 150 because Mew was hidden and was not normally obtainable through standard gameplay. Mew was nevertheless part of the original Pokédex numbering and is officially Pokémon number 151.
Later generations expanded the Pokédex with new species, but the first 151 remain especially recognizable. The “Gotta Catch ’Em All” idea became one of the franchise’s defining messages and helped turn collecting into Pokémon’s central activity.