Mew is National Pokédex number 151, making it the final species in the original 151-Pokémon sequence.
Mew is a Mythical Pokémon associated with the first generation. In the original Game Boy games, it was not normally obtainable through ordinary gameplay. Its rarity and special-event distribution helped create rumors and secrets around the Pokémon, especially before official information was widely available online.
Mewtwo occupies number 150 immediately before Mew. The two names and their related story roles often lead to confusion, but they are separate species. Mew is described as having genetic links to many Pokémon, while Mewtwo was created through scientific experimentation based on Mew.
Mew’s position as number 151 also explains the phrase “the original 151.” The first generation began with Bulbasaur at number 001 and ended with Mew, although the games’ story and ordinary encounters did not present every species in straightforward numerical order.