Which Pokémon game was the first to let players battle Pokémon in 3D on Nintendo 64?

Pokémon Stadium was the first Pokémon game to let players battle in 3D on Nintendo 64.

Released in Japan in 1999 under the international Pokémon Stadium name after an earlier Japanese title, the game translated the handheld battle system into fully modeled 3D arenas. Players could select teams, watch attacks animate, and compete in tournament-style challenges.

A bundled Transfer Pak allowed compatible Game Boy Pokémon to be used with the Nintendo 64 game. This feature connected the handheld and console versions instead of treating them as completely separate experiences.

Pokémon Snap also appeared on Nintendo 64, but it is a photography game rather than a battle-focused title. Pokémon Colosseum and Pokémon Battle Revolution came later on newer Nintendo consoles, so they were not the first 3D Pokémon battle games.