Which Pokémon game was the first to feature all 151 original Pokémon in 3D battles?

Pokémon Stadium was the first Pokémon game to feature all 151 original Pokémon in 3D battles.

Released for the Nintendo 64, Pokémon Stadium presented battles using polygonal 3D models rather than the sprites used in the Game Boy games. It allowed players to use the full original Pokédex from Pokémon Red, Blue, and Yellow, making the first-generation Pokémon visible in a new visual format.

The game focused on competitive battles instead of a traditional role-playing adventure. Players entered Cups, challenged Gym Leaders, and used teams of up to six Pokémon, selecting three for individual battles. A Transfer Pak also connected the Nintendo 64 game to compatible Game Boy cartridges.

Pokémon Stadium is sometimes confused with the Japan-only Pocket Monsters Stadium, released in 1998. The internationally released Pokémon Stadium followed in 1999 in Japan and in 2000 in Western regions. Its minigames and announcer helped distinguish it from the main series.