Pokémon League

A Pokémon League is the top-level tournament of Pokémon Trainers, who compete in Pokémon Battles toward beating increasingly higher-ranked Trainers. To enter, one must collect eight badges, one from each Gym in their regional area. Also they are only allowed to use six Pokémon at a time, both in the games and the anime. However, unlike in the games where a Trainer only works toward the goal of eventually battling the top victors, called the "Elite Four," in the anime, Trainers must participate in a tournament where they battle one another.

Kanto
In the Kanto region, it is located in the Indigo Plateau pass the Kanto Victory Road, which is slightly north-west of Viridian City

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

Hoenn
The Pokémon League is found at Ever Grande City in between the city player must go through the Hoenn Victory Road which is an island

Sinnoh
The Sinnoh Pokémon League is located at the north of Sunyshore City, where players have to cross the water route and enter the Sinnoh Victory Road to reach there. This marks the first time the Champion has been female.

Unova
In Black and White, the Unova Pokémon League is located northeast of Opelucid City, where players have to cross a land route and pass the Victory Road to arrive.

In Black and White Versions 2, the Pokémon League is situated eastwards of Humilau City; to arrive, the player must cross a land route briefly interrupted by the Giant Chasm and pass the Victory Road.

This marks the first time where the Elite Four (apart from the Champion) can be battled in any order, the Champion still cannot be battled until after Shauntal, Grimsley, Caitlin and Marshal have been battled. The Champion in Black 2 and White 2, Iris, is the youngest Champion at around age 12.

Kalos
The Kalos Pokémon League region is located directly northwest of Snowbelle City. The player must go to Route 21 or Route 22 in order to reach the Victory Road. The player must defeat all members of the Elite Four; Malva, Siebold, Wikstrom, and Drasna in order to defeat the champion of Kalos, Diantha.