Elemental Nation

This is when the process of defining nations in fantasy settings is to have each group be under the domain of one kind of magic. The main appeal to this is, naturally, the easy convenience of being able to define who is from what nation, since they'll have the appropriate elemental affinity to go with it, and the trappings of the culture itself will be clearly delineated by that element as well. This is often paired with tropes like Single Palette Town in order to get the full effect. On the downside, this can sometimes result in a Planet of Hats situation on a small scale, since all members of a specific nation must, by definition, fit into the general archetypes of their nation's element.

Taken to extremes, the nation can fall prey to the problem of Poor Predictable Rock.

Compare Elemental Plane.

Anime and Manga

 * Naruto has the Land of Wind, The Land of Earth, The Land of Water, The Land of Lightning and the primary setting, the Land of Fire. There are also a bunch of way smaller countries with names like the Land of Grass, the Land of Waves and the Land of Vegetables. Subverted in that many of the most powerful ninja don't use jutsu that match their nation. The Land of Fire 'is' known for their Fire Monks and the fire-using Uchiha clan, but the First Hokage was famous for using trees, and his brother was skilled at water techniques. In fact, the vast majority of ninja from the Land of Fire don't use fire, and likewise with Land of Wind ninja. This trope has so far held true with Earth, Lightning and Mist though, but then only a very few ninja from each of those countries have been shown.
 * Possibly the Land of Fire is more diverse because the Uchia clan, who has fire powers, doesn't run the show but the clans that give the names run the show in the other nations.

Literature

 * The Death Gate Cycle, though it's more of an Elemental Worlds thing there.
 * The Banned and The Banished series of books have a variety of different tribes/races associated with different elemental magic forms. Dryads and Earth, Elves and Air, Mountain tribes and Rock.
 * Employed by the Xanth series.
 * In The Great Tree Of Avalon trilogy, each of the seven elemental realms has at least one race specifically attuned to the element, even though they usually aren't its sole inhabitants (this depends mainly on how inviting it is to other races; you won't find many humans willing to settle in Shadowroot or Waterroot for example).

Tabletop Games

 * Magic the Gathering does this fairly frequently. Aligning tribes with certain colours or colour combinations, which in different blocks can be associated with differnt elements.
 * Taken to extremes in the Odyssey block (and the Onslaught block, which took place in the same setting) where the entire map was created simply by superimposing two colour wheels on the spare continent outline they had lying around.
 * And the 5 Shards of Alara were elementals worlds; Alara broke in to 5 pieces, one for each color of mana, accompanied by the two allied colors. The design of each of the shards was based off a world with only 3 colors of mana (Bant is super organized and caste based, as it lacks the chaos of red or the jockeying for position of black, for example).
 * The main setting in Exalted, Creation, has the Elemental Poles of Fire (south), Water (west), Air (north), Wood (east) and Earth (center). The closer you get to the pole, the more prominent the element becomes; the south is a vast desert and then volcanoes, the west opens to a vast ocean, and the east is thicker and thicker forests. The people naturally try to adapt.

Toys

 * Used by the Gormiti toys and TV show.
 * Bionicle: Mata Nui and Metru Nui were divided into seven regions, six of which corresponded to each element of Fire, Water, Air, Earth, Stone and Ice (the seventh was a neutral zone in the center). Bara Magna looks similar on the surface, having the same color-coding for tribes from different areas, but none of its peoples have innate elemental powers.

Video Games

 * Skies of Arcadia uses this for all the defined nations. Though "magic" figures largely as a game mechanic, the cultures are all clearly influenced by the kinds of moonstones to which they have access: Valua has a strong industrial sector powered by electricity, Ixataca has lots of trees, and Yafutoma has ships that can fly unusually high. Nasr mostly just has sand, but its people manage.
 * In The Legend of Zelda games, forest residents (Deku or Kokiri) have the Forest element; Gorons have the Fire element; Zoras have the Water element. This has more to do with their temple and artifacts than their magical abilities, since spellcasting isn't common in these games.
 * Other races connected to elements (some of which are more abstract than anything) include the Gerudo (desert/spirit), Yeti (ice/snow), the Wind Tribe (air/wind), the Sheikah (shadow), and the Twili (Twilight).
 * World of Warcraft has the Elemental Plane, another dimension (or dimensions, it's not clear) dominated by elementals of certain types. The Firelands, for example, are inhabited by hellhounds, fiery scorpions and turtles, magma elementals of several shapes, sizes and levels of intelligence, and so on. While that doesn't exactly fit this trope, in the Cataclysm expansion, the elemental place(s?) have begun to intrude on Azeroth, setting the scene for elemental invasions and stuff.
 * The Adept clans of Golden Sun fall into this, particularly the Mars Clan of Prox, the Mercury Clan of Imil, and the (functionally-extinct) Jupiter Clan of (vanished) Anemos. Lemuria would also qualify, being exclusively Mercury, though it doesn't identify as such as readily as the others. There's no sign of where or who the Venus Clan was, and Adepts of all four elements have been known to exist elsewhere.

Western Animation

 * Avatar: The Last Airbender features this prominently. Elemental "bending" is limited to characters from the appropriately named nation that engages in use of that element. Moreover, the nations themselves are easily defined by those elements. The Air Nomads, when they were still around, largely lived in high-up temples to which only they could glide. The Water Tribe lives at the poles (where they are naturally surrounded by water), except for one offshoot that lives at a swamp (which is mostly surrounded by water). The Fire Nation has an inordinately large number of active volcanoes in its territory. The Earth Kingdom, in addition to being a massive landmass, is very rocky and mountainous with lots of caves.

Web Original

 * Explicitly averted by five powers of Lambda, mostly so it doesn't end up looking like Avatar with Magical Girls, and also to avoid Poor Predictable Rock.