The original 1996 Pokémon games introduced 151 Pokémon. These species are commonly called the first generation and are numbered 1 through 151 in the original Pokédex.
The list begins with Bulbasaur, Ivysaur, and Venusaur, then continues through the Kanto Pokémon in Pokédex order. It ends with Mew, a secret Pokémon that was not openly advertised as part of the regular game experience at launch. Players generally needed trading, special events, or unusual methods to obtain every species.
Although the games contained 151 Pokémon, a player could not normally collect all of them in one version. Red and Green, and later Red and Blue internationally, had version-exclusive Pokémon. Trading through the Game Link Cable was therefore central to completing the Pokédex. Later generations expanded the total far beyond the original 151.