A Gym Leader (Japanese: ジムリーダー, Hepburn: Jimu Riidaa) is the highest-ranking member and owner of an official PokémonGym, and they serve as the main bosses of the games. Gym Leaders theme their gym and the Pokémon they use on a specific type, which also extends to the staff that work there. Blue is a unique outlier in this as he does not have a type specialty. Gym Leaders in Paldea also run a single Pokémon of a different type, although they align it with their specialty through the use of the Terastal phenomenon.
Before facing a Gym Leader, challengers have to pass a test, which can involve fighting, problem solving or a mix of both. If a trainer wins the minimum required amount of badges for a specific region's Pokémon League Conference, that is eight, they're eligible to compete — they also have the chance to battle the region's Elite Four. There are a total of eight Gym Leaders in each region, usually all eight gym leaders in a region will specialize in a different type of Pokémon, the most recurring type for the first gym is Rock due to both Grass and Water being super effective against it. Unlike regular Pokémon Trainers, a Gym Leader has the right to directly challenge the Pokémon League Champion, as revealed by Brock in Pokémon: Let's Go, Pikachu! and Pokémon: Let's Go, Eevee!.
Until Generation IX, players generally had to face the Gym Leaders in a set order. Some earlier exceptions to this existed in a limited capacity based on the player for Kanto, Johto & Sinnoh though. Generation IX's Gym Leaders can be fought in any order, but their Pokémon will not scale to the player's team.
As shown several times, a Gym Leader is usually well involved with their community. When not at the Gym, a Gym Leader is usually involved in some type of work or service that the surrounding community is known for (this is more prevalent in the anime and the manga than the video games). If the Gym Leader is unable to perform their duties, they may leave the place running by a trusted family member or subordinate. When at the Gym, a leader will maintain the Gym itself, the Pokémon, the other members, and will battle any challenger.
The Gym Leaders in Paldea are known to go through periodical Gym Inspections every year, usually by a Champion to ensure that they're doing their job correctly. If the inspection is deemed a failure, the Gym Leader would lose their position.
While Brock begins as the Gym Leader, his father: Flint, is the former Gym Leader, his mother: Lola took over the gym and made it a Water-type Gym, and his younger brother Forrest is the current Gym Leader.
Route to Vermilion City[]
While Ash travels and meets the Gym Leaders from the games as normal, he also meets a trainer named A.J., who runs his own unofficial Gym which is on the route to Vermilion City, A.J.'s gym does not have a badge or a type.
A.J. also makes a brief appearance in the games as a Youngster on Route 9.
Vermilion City[]
While Lt. Surge is the current Gym Leader, he left on a quest to train himself sometime prior to the events of the Journey series, having Visquez serve as the Acting Gym Leader in his absence.
Cerulean City[]
While Misty is the current Gym Leader, her three sisters: Daisy, Violet, and Lily act as Gym Leaders until Misty takes the post.
Viridian City[]
While Giovanni starts as the Gym Leader like in the games, he has to go on a business journey - so he leaves Jessie, James, and Meowth as the Gym Leaders. Jessie is the one who actually does the battling.
Since Giovanni does not return from the business trip as he is busy running Team Rocket, the Elite Four member Agatha is put in charge of the Gym.
Orange Islands[]
The Gym Leaders from the Orange Islands have only appeared in the Pokémon Anime series and not in game series. In addition to this, these Gym Leaders work slightly differently than others, usually having trainers that face them take part in a number of challenges rather than Pokémon Battles. Also, the majority of these Gym Leaders do not specialize in a specific Pokémon type.
Clemont built a robotic version of himself called Clembot to run the Gym for him when he was too busy to attend his duties as a Gym Leader. After Clembot went "rogue" (due to an accident during programming), Clemont managed to regain control of Clembot after defeating it in a match. Clemont later reprogrammed Clembot to be friendlier and had it serve as the Acting Gym Leader while he went travelling across Kalos with his friends.
Trivia[]
The Dark type is the last type to receive a Gym Leader specializing in the type with the introduction of Piers and Marnie in Generation VIII.
The only regions with Gym Leaders for all three of the starter types are Kanto, Unova and Galar.
However, in the Generation V games, the player character is only able to have a Gym battle with the Gym Leader for one of those types (starter's weakness in Black and White; Water in Black 2 and White 2).
Johto is the only region with no Gym Leaders that specialize in any of the starter types.
Due to the Hoenn and Unova regions having two Water-type Gym Leaders each (Wallace and Juan; Cress and Marlon), there are a total of six Gym Leaders of this type, more than any other type.
However, the type with Gym Leaders in the most regions is Electric, with a Gym Leader of that type in every region except for Johto and Galar.
Also, while Tate and Liza both specialize in Psychic-type Pokémon, Cilan and his two brothers each specialize in a different type of Pokémon: Cilan specializes in Grass types, Chili specializes in Fire types and Cress specializes in Water types.
While Cilan, Chili and Cress each fit the criteria of Gym Leaders specializing in only one specific type of Pokémon, the Striaton City Gym is the only gym to technically specialize in more than one type of Pokémon.
All of the Galar Gym Leaders have a special ID Number on their jersey. All of these are numbers can be translated from Japanese Pager Code to say a word relating to them:
Milo has the number 831, which translates to ya-sa-i, meaning 'veggie'.
Nessa has the number 049, which translates to o-yo-gu, meaning 'swim'.
Kabu has the number 187, which translates to hi-ba-na, meaning 'spark'.
Bea has the number 193, which translates to i-ku-sa, meaning 'fight'.
Allister has the number 291, which translates to ni-ku-i, meaning 'detest'.
Gordie has the number 188, which translates to i-wa-ba, meaning 'rock wall'.
Melony has the number 361, which translates to sa-mu-i, meaning 'cold'.
Opal has the number 910, which translates to kyu-to, meaning 'cute'.
Piers has the number 061, which translates to wa-ri-i, meaning 'bad'.
Raihan has the number 241, which translates to tsu-yo-i, meaning 'strong'.
In the Paldea region you can tackle the gyms in any order, but the Gym Leaders Pokémon levels do not scale to suit the challenger.