Mew was the first Mythical Pokémon introduced in the Pokémon series.
Mew is a Psychic-type Pokémon from Generation I and is numbered 151 in the original Pokédex. It was designed as a mysterious, extremely rare creature that could be obtained only through special events in the earliest games rather than through ordinary gameplay.
The character’s secrecy helped create rumors around the original Pokémon games. Mew was added late in development, and its presence was not widely publicized when Pokémon Red and Green launched in Japan. Players later learned about it through official distributions, contests, and promotional events.
Mewtwo is often confused with Mew because its name and origin are connected. Mewtwo is a Legendary Pokémon engineered from Mew’s genetic material, while Mew is the earlier Mythical Pokémon. “Mythical” is a later classification used for rare event-associated Pokémon, so older sources may simply describe Mew as legendary or secret.