Mew is National Pokédex number 151, the final entry of the first generation.
Mew is a Psychic-type Mythical Pokémon introduced alongside the original Kanto roster. Its small, pink, catlike design and ability to learn many moves made it especially mysterious to early players. Mew was not normally obtained through standard gameplay in the original games, which helped fuel rumors and speculation about how to find it.
Mewtwo is number 150, immediately before Mew. Despite the similar names and related backstory, they are separate Pokémon: Mewtwo is an engineered clone created from Mew’s genetic material, while Mew is presented as an ancient and exceptionally rare species. Celebi and Arceus belong to later generations and cannot be the final entry of the original 151.
Mew’s hidden presence became an important part of Pokémon’s early history. Satoshi Tajiri revealed the extra Pokémon after development, believing its existence would create rumors and sustain interest. Its position at number 151 has made Mew a memorable endpoint for the original Pokédex.