A lot of people say that Sinnoh is based on Hokkaido, and there's certainly a lot of evidence to support it (probably the biggest is the correlation of the 3 Sinnoh lakes to Lakes Toya, Kussharo, and Kutcharho, as well as Mt. Coronet paralleling with the Ezo mountain range).
But recently, I had a thought. I live in Canada, and I know a fair bit about the place, if I do say so myself.
My thought was that Sinnoh was, at least partially, based on Sinnoh. I noticed that, hey, there's not a whole lot of evidence or support for my theory. Probably because I'm the first one to have it.
Here's a map of Canada for reference while reading this post.
And here's my map with labels showing the similarities between Sinnoh and Canada.
Region 1, Iron Island, is the Yukon. Yukon is known for its gold production during the Gold Rush.
Region 2, Fullmoon Island and Newmoon Island, are Banks Island and Victoria Island, located in upper Nunavut.
Region 3, Snowpoint City and the surrounding area, is basically Nunavut and the Northwest Territories.
Region 4, the Battle Zone, is Greenland! It's exactly in the right spot.
Region 5 is based mostly on Ontario and Manitoba - note the rivers running through it towards Region 6.
Region 6 is, of course, the Great Lakes. That part that juts out into the ocean is very similar to the one in Ontario that kind of spears between Lake Huron and Erie.
Region 7 is the Rocky Mountains, just pushed to the center a bit.
Region 8 is basically British Columbia, and Alberta kind of being shoved to the left of the Rockies. Oreburgh City parallels Drumheller, a town known for its dinosaurs. Canalave is Victoria (note how you have to get there by water), Jubilife is Vancouver and/or Edmonton. Eterna and Floaroama are referencing the farmlands.
Region 9 is Québec. The mountains or whatever there parallel the Laurentians.
Region 10 is eerily similar to the Hudson Bay.
Region 11 (the Elite Four Island) is Newfoundland.
Region 12, Sunyshore City, is Halifax. It's on the coast. And wanna know something really crazy? You know that island with the lighthouse that you can only access by the solar roads. Well, look at the coast of Halifax, with a convenient little chunk of land off the coast. Oh, and look at that in the background. A LIGHTHOUSE.
And finally, Region 13 is a little (pun intended) shout-out to Prince Edward Island.
Plus, this is kind of obvious and a huggeeeee Canadian stereotype, but Sinnoh is pretty damn cold.
Also, even though she's English in the Japanese version, it might be worth noting that Fantina is French. Whether that be the translators acknowledging these parallels, who knows.
Thanks for your time.