Which main-series Pokémon games were the first to feature entirely 3D graphics?

Pokémon X and Y were the first main-series Pokémon games to feature entirely 3D graphics.

Released for the Nintendo 3DS in 2013, the games replaced the primarily sprite-based presentation of earlier main-series entries with fully 3D environments, characters, battles, and Pokémon models.

The games take place in the Kalos region, which is inspired by France. They also introduced the Fairy type, Mega Evolution, character customization, and new online features through the Player Search System.

Earlier Pokémon titles had already used 3D elements. Pokémon Stadium, for example, presented battles in 3D, but it was a spin-off rather than a main-series role-playing game. That distinction is why X and Y hold this particular milestone.