Which two Pokémon types debuted in Pokémon Gold and Silver?

Dark and Steel were the two Pokémon types introduced in Pokémon Gold and Silver.

Released in Japan in 1999 for the Game Boy Color, Gold and Silver formed Pokémon's second generation. The new types expanded the battle system and added fresh strategic relationships beyond the original generation's type chart.

Dark-type Pokémon were designed around sinister or underhanded techniques and gained special importance against Psychic-type Pokémon. Steel-type Pokémon emphasized defensive strength and resistance, creating new tactical possibilities in battles.

The games also introduced 100 new Pokémon, the Johto region, breeding, held items, a day-and-night cycle, and the ability to revisit Kanto after completing the main Johto adventure. Fairy type did not appear until Pokémon X and Y in 2013, which is why it is not one of the second-generation additions.