Pokémon League

Pokemon League
Pokemon League is a center where all pokemon trainer comes to battle the leaders of all trainer. To enter you have to collect all of the badges.

Kanto
In the Kanto region, it is located in Indigo Plateau, where the Elite Four are Bruno, Lorelei, Agatha and Lance. The champion will be your rival (he looks like the character in the anime, Gary).

For Pokémon Gold/Silver/Crystal, it would be Will, Koga, Bruno, Karen and the champion Lance.

Johto
There is no Pokémon League in Johto. You have to cross the water route next to New Bark Town to Indigo Plateau. Refer to Kanto above.

Hoenn
The Pokémon League is found at Ever Grande City. The Elite Four are Sydney, Phoebe, Glacia, Drake. The champion for Pokémon Ruby/Sapphire is Steven while the champion for Pokémon Emerald is Wallace.

Sinnoh
The Pokémon League is located at the north of Sunyshore City, where players have to cross the water route and enter the Victory Road to reach there. The Elite Four are Aaron, Bertha, Flint, Lucian and the champion is Cynthia.