What was the name of the Japan-only Nintendo 64 game released before Pokémon Stadium?

The Japan-only Nintendo 64 game released before Pokémon Stadium was Pocket Monsters Stadium.

Nintendo released Pocket Monsters Stadium in Japan on August 1, 1998. It was developed by Nintendo EAD and provided three-dimensional Pokémon battles on the Nintendo 64, connecting with the original Game Boy games through the Transfer Pak.

The game supported only 40 Pokémon in battle, rather than all 151 available in the Game Boy games. Technical limitations affected the roster, and the title was never released outside Japan. Its restricted availability is why many international players have never encountered it.

The internationally released Pokémon Stadium followed in 1999 in Japan and in 2000 elsewhere. In Japan, that later game was initially known as Pokémon Stadium 2, which creates a numbering trap: the Japan-only Pocket Monsters Stadium is the first game in the series, while the internationally familiar Pokémon Stadium is effectively its expanded successor.