Which Nintendo 64 Pokémon game first allowed battles using all 151 original Pokémon?

Pokémon Stadium was the Nintendo 64 Pokémon game that first allowed battles using all 151 original Pokémon.

Released in Japan in 1999, Pokémon Stadium presented Pokémon battles in 3D and connected with Pokémon Red, Blue, and Yellow through the Nintendo 64 Transfer Pak. Players could upload Pokémon from their Game Boy cartridges for battles and other features.

The title can be confusing because Japan had an earlier game called Pocket Monsters Stadium in 1998. That earlier release allowed only 40 of the original 151 Pokémon in gameplay. The later game was released internationally as Pokémon Stadium, while Japan treated it as Pokémon Stadium 2.

The international version arrived in 2000 and became one of the best-selling Nintendo 64 titles. Its full 151-Pokémon battle roster, voice announcements, minigames, and compatibility with the handheld games helped define Pokémon's early move into 3D.