Which Pokémon generation introduced the greatest number of new species?

Generation V introduced the greatest number of new Pokémon species, with 156.

The generation debuted in Pokémon Black and White, released for Nintendo DS in 2010. Its Pokédex ran from Victini at number 494 to Genesect at number 649, creating the largest single-generation addition to the franchise’s species list.

Generation V was unusual because Pokémon Black and White initially restricted the player to newly introduced species before the post-game. This gave the games a fresh cast and made the new Pokémon feel distinct from earlier generations.

The generation’s total is sometimes confused with Generation I’s 151 species, because the original games remain the most culturally prominent. Generation V exceeds that total by five, making it the largest generation by newly introduced species.