From Bulbapedia:

A Gym Leader (Japanese: ジムリーダー Gym Leader) is the highest ranking member of a Pokémon Gym. The main job of a Gym Leader is to test Trainers and their Pokémon so that they are strong and resourceful enough to compete against the Elite Four in the games or the Pokémon League in the anime. If a Trainer defeats a Gym Leader in battle, then the Trainer earns that Gym's Badge. Once a Trainer has earned 8 badges from a region, he or she is able to compete against that region's Elite Four or Pokémon League.

A Gym Leader's job is not just to test upcoming Trainers. They must oversee how their respective gym is run and to maintain it. Great care must be taken to make sure that their gym reflects the best environment for the Pokémon type and playing style of choice, usually an environment that suits that type of Pokémon used there (like pools in a Water-type gym or flowers and plants in a Grass-type gym). According to Morty, teaching young people how to battle with Pokémon can also be the job of a Gym Leader. In the games, Trainers must overcome various obstacles and challenges from other Trainers before they can challenge the Leader. Gym Leaders may also be involved in other activities when they are not battling other Trainers or training themselves, usually something to do with their town's particular attraction or landmark. Gym Leaders can also leave their gyms without notice (as Blue, Giovanni, Jasmine, and Wallace do), and even challenge other Gyms and the Elite Four (like Volkner wanted to do). In later games, it is made apparent that Gym Leaders know each other and are acquainted with Gym Leaders from other regions, and some travel to other regions: Jasmine travels to Sinnoh to take part in Super Contests, and is friends with Erika.

It has not exactly been made clear how Gym Leaders attain their position, but it appears that it varies for each gym. Some of them founded their gym and are self-appointed, others appear to be passed on through families, while a few are chosen by the other members of the region's Pokémon League. Leaders can also choose to vacate their position: reasons for this can vary. Blue is a former Champion appointed to be leader of Viridian Gym when Giovanni vacates the position, while in the anime Agatha takes Giovanni's place as a temporary leader. Koga was the leader of Fuchsia Gym until he was promoted to a member of the Elite Four; his daughter Janine replaces him as the leader. Wallace vacated his position in Sootopolis Gym when he became Champion, leaving his mentor Juan to take his place. Falkner's father is also mentioned to have been the leader of Violet Gym before Falkner took the position. Roark's father Byron is a Gym Leader like Roark himself, but the two operate entirely different Gyms within the same league.

Sinnoh is the only region where all the Gym Leaders are in cities, unlike previous generations where at least one is in a town.

In Pokémon Adventures, Red and Falkner have to battle with Pokémon set by the Pokémon League, where those Pokémon are not controlled by Trainers and the challenger is not allowed to let any of his Pokémon faint.

Although similar in nature, Frontier Brains are not considered Gym Leaders and are thus not included in this list.

Kroel Gym LeadersEdit

Overall, there are 16 Gym Leaders in the Kroel Reigon. They are divided into two groups, North and South, each consisting of eight Gym Leaders. Note that none of the Gym Leaders share the same type or any of the same Powermon.

Northern RegionEdit

The eight Gym Leaders of the Northern Region were designed by Darksilvania. They are notable for being more formal than their Southern counterparts, and most have at least one personality aspect that makes them seem menacing.

Name Type Badge City Main Powermon Other Powermon Theme
Pollock Poison Waste Badge Cauldron City Polustrial

Vermingo Opesttum Epidenza Smokroach

Industrial CEO
Artie Ice Artic Badge Frostbite City Polanoir Hyemalaya Narvharil Elephoreal Glaciartle Artic Explorer
Smith Fire Smithy Badge Brimstone City Py-Rex Centagirow Erymantoar Octanoleo Benzegatol Blacksmith
Ellie Electric Overcharge Badge Boltstrike City Smilorm Ampereohm Electrium Courobolt Voltortle Rebel Rocker
Amelia Flying Honor Badge Jetstorm City Penguealth Staglaizer Cranigami Atrimawk Bucefaloon Air Force Fighter Pilot
Necro Ghost Ghoul Badge Memorial City Judorpse Zombestein Infargeist Zonvodou Natchop Surgeon
Jack Dragon Nightwing Badge Blackfall City Consteladon Wyferno Draizelisk Notredoyle Fanbbeloki Dragon Master
D-S Dark Fiend Badge Ebony City Lucefidon Atrocean Nigtmalije Geminus Arkamera Darkness Warrior

Southern RegionEdit

The eight Gym Leaders of the Southern Region were designed by FawkesTheSkarmory. They are more informal than their Northern counterparts, and most are usually more friendly. All of the Southern Gym Leaders, with the notable exception of Michael, are based off fictional characters outside of the Pokémon franchise.

Name Type Badge City Main Powermon Other Powermon Theme
Hakoda Water Deepsea Badge Piscis City Suborca

Hiposeilor Corivancer Dracuda Venotreme

Deepsea Explorer
Tak Grass Shaman Badge Pupanunu City Totemage Fungila Bamboon Bellustona Croconstro Jungle Shaman
Michael Psychic Vision Badge Motown City Psikosiko Amphigolb Dementis Caphydring Gryphortle Pop Singer
Barnum Rock Jurassic Badge Triassic City Omakapi Stegorch Sharkarus Raptouka Mossiloth Paleontologist
Pebbles Ground Terrain Badge Bedrock City Ankrash Ocellorkey Subterosco Incalperor Zeurino Wilderness Defender
Parker Bug Antenna Badge Chelicera City Cavaliant Ignisect Terrapede Plagust Momorotha Entomologist
Juniper Fighting Harmony Badge Orchid Bay City Galludight Primareal Licab Thundare Iguaneleon Martial Artist
Robert Steel Justice Badge Metroville City Wolverusk Donferrote Majarafant Mirridel Hydraghing Superhero

See AlsoEdit

Gym Leaders in the existing Pokémon games