kanto, johto, hoenn, orre, fiore, sinnoh, almia, oblivia, unova, & kalos
although 4 of these don't have champions due to the size of 3 of them & the harsh landscape of the third. their still regions that are canon
additionally, orre's landscape isn't the only harsh aspect. area 10 of mt battle is by all means harsher then taking on the e4. each of the trainers in that area are made to be able to take on e4 members 1-1 & have an edge over them. orre may not have gyms or an e4, but the colluseums put the gym leaders to shame & mt battle puts the e4 & victory road to shame
but only 5 of them has its own regional E4 and Champion.
which mean there are only "5 Active Champion".
Among them , 2 of them are male and 3 of them are female-
Kento/Jotho : Lance
Hoenn : Wallace
Sinnoh : Cythia
Unova : Iris
Kalos : Diantha
wallace was only a champion in emerald. i still think that emerald, yellow & crystal run on a 3ed separate timeline.
besides, by the timeline nintendos currently using steven is still hoenn's champion
cynthia may be champion, but she sure as hell ain't active in her own region half the time.
the champions are considered champions until their beaten in an official match after the challenger beats the e4 under the champion.
also, cynthia is the only one known to remain known as a champion after the events of the games she's in. lance was the johto champion, not the kanto one. its stated by blue not only that red was still the kanto champion, but also that the player character was the johto champion.champions are known to leave the square rooms that lay right before the halls of fame.
hell, cynthia can show up anywhere from transitional ruins to a small ice cream stand in unvova