A Gym Leader is the highest-ranking member of a Pokémon gym. They are battled to make sure that a trainer is ready for the Pokémon League. If a trainer beats a Gym Leader in battle, they earn the Gym's respective badge. Reborn has 18 gym leaders, one for each type, along with various backup leaders.
- Victoria is the Reserve Fighting-type Gym Leader.
- Sandy is the Reserve Ground-type Gym Leader.
- Samson used to be the Reserve Fighting-type Gym Leader.
- Corey and Cain are former Poison-type Gym Leaders.
- Kiki was a former Fighting-type Gym Leader.
- Blake is a former Ice-type Gym Leader.
- Cal is a former Fire-type Gym Leader.
- Caroline and Monty, parents of Charlotte and Saphira, were the former Fire- and Dragon-type Gym Leaders.
- Fern was the Reserve Grass-type Gym Leader in previous versions. He is no longer so in Episode 19.
- After the events of the postgame, Fern replaces Florinia as the Grass-type Gym Leader and sets up a gym in Neoteric Isle, as shown in his postgame credits scene.
- According to Elias, whenever Caroline and Monty were bored, they would switch gyms and types without informing anyone.
- In Another Time, Titania and Luna were promoted to the Elite Four. Charlotte became the new temporary Ice-type gym leader after Serra's resignation, and resolved to be the permanent Fire-, Ice-, and Fairy-type Gym Leader all at once.