Bulbasaur’s National Pokédex number is 001.
Bulbasaur is the first entry in the original Pokédex and the first of the three selectable partner Pokémon in Pokémon Red, Green, Blue, and their remakes. It is a dual Grass- and Poison-type Pokémon.
Its design combines a small, squat animal with a plant bulb on its back. The bulb stores nutrients and develops as Bulbasaur grows, eventually becoming Ivysaur and then Venusaur.
The number 001 identifies Bulbasaur in the National Pokédex, not merely in a regional list. The original first generation contains 151 species, ending with Mew at 151. This ordering is why Bulbasaur is often described as the first Pokémon, even though other creatures may appear earlier in a game’s story or artwork.