Which Pokémon game introduced the ability to battle in pairs?

Pokémon Ruby and Sapphire introduced double battles to the main Pokémon game series.

In a double battle, each side can have two Pokémon active at the same time. This expanded the battle system beyond the traditional one-on-one format and made move targeting, team combinations, abilities, and battlefield effects more important.

The mechanic debuted with Ruby and Sapphire on the Game Boy Advance in 2002. It worked especially well with the generation’s new abilities and weather effects, allowing players to build strategies around combinations rather than relying on a single Pokémon’s strength.

Double battles are sometimes associated with later competitive formats, but they began in the Hoenn games. Subsequent generations retained the mechanic and used it in story battles, Trainer encounters, and official competitions. The feature helped establish Pokémon battling as a system with deeper tactical possibilities than the early games suggested.