Generation IV introduced 107 new Pokémon.
The generation began with Pokémon Diamond and Pearl for the Nintendo DS, followed by Pokémon Platinum. Its main setting was the Sinnoh region, a land that drew heavily on the geography and mythology of Japan's Hokkaido island.
The additions raised the National Pokédex total from 386 to 493. Generation IV introduced Pokémon such as Turtwig, Chimchar, Piplup, Dialga, Palkia, Giratina, and Arceus. It also expanded the evolution families of several earlier Pokémon, including new evolutions for Electabuzz, Magmar, Rhydon, and Eevee.
The figure is distinct from the number of Pokémon in individual games or regional Pokédexes. Generation IV's 107 refers to species newly introduced across that generation, not the total number obtainable in Diamond, Pearl, or Platinum.