Which two games first introduced Pokémon’s Johto region?

Pokémon Gold and Silver first introduced Pokémon’s Johto region.

Johto is the setting for the second generation of the main Pokémon video game series. The region appeared in Pokémon Gold and Silver, which added 100 new Pokémon, a day-and-night system, breeding, and other major features.

Johto is connected to Kanto, the region from the first-generation games. After completing the main story in Gold and Silver, players can travel through Kanto, making the games unusually large and linking the first two generations directly.

Pokémon Crystal later expanded the same generation with additional story material and the Battle Tower. Remakes titled Pokémon HeartGold and SoulSilver brought Johto back to the Nintendo DS with updated graphics and mechanics.