Niantic have announced that 23 additional Pokémon originally discovered in the Hoenn region have been added to Pokémon GO.

More Pokémon originally from the Hoenn region are here!

Trainers, Starting later today, 23 additional Pokémon originally discovered in the Hoenn region in the Pokémon Ruby and Pokémon Sapphire video games will begin appearing in Pokémon GO for the very first time. As you’re out adventuring with friends and family and exploring your local neighborhoods, be sure to share your favorite moments and photos using #PokemonGO on your social media channels.

Source: https://pokemongo.nianticlabs.com/en/post/hoenn-pokemon-012318/