Hoenn first partner Pokémon, otherwise known as Hoenn starter Pokémon, are Pokémon chosen by Trainers at the start of their journey in Hoenn. These are traditionally given out by Professor Birch and are to be used to battle the first wild Pokémon that the Trainer encounters.
In the core series Hoenn-based games, the player can choose a Fire-, Water-, or Grass-type first partner Pokémon at level 5.
The player's neighbor, Brendan or May, already has their first partner Pokémon, which is always the one with the type advantage. By the end of Ruby, Sapphire, and Emerald, it seems that the player's nominal rival, the son/daughter of Professor Birch, has stopped being a Trainer, and Wally is actually the true rival, facing the player before they can leave Victory Road and staying there to have rematches with the player later. In Omega Ruby and Alpha Sapphire, Brendan or May's role as an NPC is slightly expanded, acting as a post-credits battle in which they gain access to Mega Evolution for their first partner Pokémon.
The Hoenn first partner Pokémon; owned by Brock, Ash, and May from left to right
In the anime
in the main series
During the Hoenn arc of the main series, Professor Birch gave away four of the three first partner Pokémon to new Trainers. Harrison and May both received a Torchic and Sawyer began his journey with a Treecko. Although Professor Birch isn't seen gifting a Mudkip to any Trainers, in A Mudkip Mission, Mudkip BreederOld Man Swamp revealed that Professor Birch is also responsible for the breeding and raising of the young Mudkip for new Trainers.
In the manga
Ash & Pikachu
In the Ash & Pikachu manga, Professor Birch gives a Torchic to May.
Pokémon Adventures
In Pokémon Adventures, Professor Birch gifts a Torchic to Sapphire and a Mudkip to Ruby. Professor Birch was also revealed to be in possession of a Treecko, however the Pokéball containing the Pokémon was washed away in a flood. It was later found by Wally, and eventually came to be under the ownership of Emerald.
Pokémon Pocket Monsters
In Pokémon Pocket Monsters, Professor Birch is in possession of the three Hoenn first partner Pokémon to which he gifts to new Trainers. The only one he is seen giving out though is a Torchic which he gives to Sapphire.