Which pair of Pokémon games introduced the Kalos region?

Pokémon X and Y introduced the Kalos region.

Released worldwide for the Nintendo 3DS on October 12, 2013, Pokémon X and Y are the first main-series Pokémon games to use fully polygonal 3D graphics for the overworld and battles. Their setting, Kalos, is inspired by northern France and includes locations such as Lumiose City.

The games added the sixth generation of Pokémon and introduced mechanics including Mega Evolution, which temporarily changes certain Pokémon during battle. They also added the Fairy type and Pokémon-Amie, a feature for interacting with Pokémon.

Kalos is sometimes confused with Galar or Paldea, the settings of later main-series games. Pokémon X and Y are specifically associated with Kalos, while Pokémon Sun and Moon use Alola and Pokémon Sword and Shield use Galar.