Generation V introduced the highest number of new Pokémon species in a single generation.
Pokémon Black and White introduced 156 new species, more than any other generation. The games are set in the Unova region and initially emphasize their new roster by limiting access to earlier Pokémon during the main story.
Generation V’s additions include the starters Snivy, Tepig, and Oshawott, as well as major Legendary Pokémon such as Reshiram, Zekrom, and Kyurem. Victini is the first entry in the Unova Pokédex, although its National Pokédex number is 494.
The record can be confused with Generation I, which established the original 151 Pokémon and remains the best-known starting roster. Generation IX added a large number over several releases, but its total was divided across the base games and downloadable content rather than matching Generation V’s single-generation introduction.