In the Pokémon franchise, which species is National Pokédex #001?

In the Pokémon franchise, Bulbasaur is National Pokédex #001.

Bulbasaur is a dual-type Grass/Poison Pokémon introduced in the 1996 Game Boy games Pocket Monsters Red and Green. It is one of the three selectable starting Pokémon in the Kanto adventure, alongside Charmander and Squirtle.

Its Pokédex number identifies its position in the National Pokédex, the numbering system that brings Pokémon from different regions together. Bulbasaur is also the first entry in the original regional Pokédex used for the Kanto games.

A common mix-up is confusing Bulbasaur with Ivysaur, its evolved form. Bulbasaur evolves into Ivysaur at level 16, and Ivysaur later evolves into Venusaur at level 32. The species is recognizable by the plant bulb growing on its back, which develops as it grows.