Which Nintendo 64 game first let players battle with all 151 original Pokémon?

Pokémon Stadium was the Nintendo 64 game that first let players battle with all 151 original Pokémon. It was released in Japan in 1999 and later in Western regions in 2000.

The game presented Pokémon battles in 3D, using turn-based combat adapted from the Game Boy titles. Players could also connect Pokémon Red, Blue, and Yellow cartridges through the Transfer Pak and use Pokémon raised in those games.

A Japan-only predecessor, Pocket Monsters Stadium, had featured a much smaller selection of Pokémon. Pokémon Stadium expanded the roster to all 151 species, making it the major home-console showcase for the first generation.

The title included Cups, Gym Leader Castle, multiplayer battles, and mini-games. Its sequel, Pokémon Stadium 2, added compatibility with Pokémon Gold, Silver, and Crystal and expanded the available roster.