The original Generation I Pokémon lineup contained 151 species.
These Pokémon debuted in the 1996 Game Boy games Pocket Monsters Red and Green, later known internationally as Pokémon Red and Blue. Their National Pokédex numbers run from Bulbasaur at 0001 to Mew at 0151.
The number 151 was the original completion target for the first-generation Pokédex. The games’ central appeal involved discovering, catching, training, evolving, and trading these creatures. Because some Pokémon were exclusive to one version, players needed trading or special events to complete the collection.
A frequent mix-up concerns the number available in the initial game files or early marketing. The Generation I Pokédex officially contains 151 species, including the secret Mythical Pokémon Mew. MissingNo. is a famous glitch and is not an official species in that count. Later generations expanded the total substantially.