Kanto is a region in the Pokémon universe it was followed by Johto, Hoenn, Sinnoh, Unova, Kalos and Alola. It is modeled and named after the Kantō region, a region in Japan, which includes, amongst other cities, the Japanese capital Tokyo and as all the other regions weren't named after somewhere Kanto is the only one that shares its name with a real world location. It was the first region released. The resemblance between the bay formations seen on the in-game map and the actual Sagami Bay, Suruga Bay and Tokyo Bay formations is particularly striking.
Kanto lies to the east of Johto; they presumably make up a small continent. South of Kanto are the Orange Islands. Hoenn, introduced in Pokémon Advanced Generation, is supposedly further to the southwest. Routes located wholly within Kanto are numbered 1 to 25; routes 26, 27 and 28 connect Kanto with Johto. Supposedly to the north of this continent is the Sinnoh region. Unova is a considerable distance away and it's unknown where both it and Kalos are in relation to Kanto.
In the first series, Pokémon: Indigo League, Kanto was the only explore region, featuring a variety of environments, such as urban locales and mountainous, wooded and oceanic routes. In Pokémon: The Johto Journeys, Pokémon: Johto League Champions and Pokémon: Master Quest, Ash Ketchum and his friends travelled to Johto after adventuring through the Orange Islands.
During the episodes after the Hoenn League of Pokémon: Advanced Battle and during Pokémon: Battle Frontier Ash Ketchum, Brock. May and Max travel here to collect Frontier Symbols and Contest Ribbons and Misty does travel with them until they reach the crossroad between Cerulean City and the way to the Battle Factory.
During the last 2 episodes of Pokémon: BW Adventures in Unova and Beyond when Ash Ketchum, Iris, Cilan and the Journalist Alexa from Kalos arrive in Kanto and Iris and Cilan say their goodbyes because they instantly go off to Johto (Iris goes because she wants to see Clair the Dragon-type Gym Leader of Johto who lives in Blackthorn City and Cilan goes because he wants to go to Hoenn for a Fishing Competition) after Ash Ketchum and Alexa say goodbye to Iris and Cilan and the train has left they head to Pallet Town where Ash decides to go to Kalos with Alexa which by doing so he will get a trip down memory lane (despite it takes until he sees something for that to happen).
For the list of Kanto's Gym Leaders click here.
For the list of Kanto's Elite Four members click here.
For Kanto's Champion click here.
For the list of the Notable people that have visited Kanto click here.