Mew is number 151 in the original Pokémon Pokédex.
The first Pokémon games contained 151 numbered species, from Bulbasaur at number 001 to Mew at number 151. Mew is a Mythical Pokémon associated with genetic ancestry and is described in the games as having the genetic composition of all Pokémon.
Mew was not normally obtainable through standard gameplay in the original releases. It was distributed through special events and promotions, which helped create a lasting air of mystery around the final Pokédex entry.
Mew is often confused with Mewtwo because Mewtwo is number 150 and is linked to Mew in the games' story. Mew is the earlier Pokédex number, while Mewtwo is the laboratory-created Pokémon connected to Mew's genetic material.