Dungeons & Dragons
Dungeons & Dragons was derived from miniature wargames and is commonly recognized as the beginning of modern role-playing games, remaining the most-known tabletop RPG in the US.
Created by author and game designer Ed Greenwood as his personal campaign and detailed in a long series of articles in Dragon Magazine, The Forgotten Realms is a high fantasy world - magic is powerful, legendary monsters are commonplace, and gods often intervene directly in mortal affairs. It has become the most popular D&D setting from the late 1980s onwards and is the default setting for most adventures released for D&D 5th Edition, though more recent books have shifted to reference the wider multiverse.
A shared universe created by Laura and Tracy Hickman, and expanded by Tracy Hickman and Margaret Weis, Dragonlance is an epic fantasy campaign focused on a war between good and evil gods and the return of dragons after centuries of absence. Dragonlance was the first complete fictional world to be intentionally produced and marketed as an RPG supplement, with product tie-ins (novels, role-playing modules, figurines, etc.) prepared and manufactured when it was first released. The success of the Dragonlance series encouraged role-playing game producers to invent and market additional fictional game worlds.
Originally published for the Advanced Dungeons & Dragons 2nd Edition, Spelljammer is set in "wildspace", a fantastical version of outer space based on classical notions of the universe in which magic-imbued ships interact with each other and locations in space, designed to allow the usual sword and sorcery adventures of Dungeons & Dragons to take place within the framework of outer space tropes. Flying ships travel through the vast expanses of interplanetary space, visiting moons and planets and other stellar objects, unifying most of the other AD&D settings and providing a canonical method for allowing characters from one setting (such as Dragonlance) to travel to another (such as the Forgotten Realms), while keeping all of the action on the Prime Material Plane.
A gothic horror setting originally created by Tracy and Laura Hickman for their own game system, ravenloft was expanded into an entire series of adventure modules and then further expanded into a campaign setting and novel series. Ravenloft made it into 5th edition first in the adventure module Curse of Strahd, written by the setting's original creators, and more recently in the campaign sourcebook Van Richten's Guide To Ravenloft which revised the setting to include a variety of different horror genres in addition to gothic horror and purge the misogynistic, colonialist, or racist elements that were present in Ravenloft's prior iterations.
Originally created by Matthew Mercer for his personal campaigns in 2012, Exandria is a high fantasy setting that moves away from the harmful tropes in D&D around monstrous races and is where the Critical Role web series is set. Exandria was first mentioned in an official Wizards of the Coast publication in the adventure module Baldur's Gate: Descent Into Avernus, and later expanded upon in the campaign sourcebook Explorer's Guide to Wildemount which focuses on the continent of Wildemount where the second Critical Role campaign takes place.
Created by author and game designer Keith Baker as the winning entry for Wizards of the Coast's Fantasy Setting Search, a competition run in 2002 to establish a new setting for D&D, Eberron combines a fantasy tone with pulp and dark adventure elements, and some steampunk-esque fantasy technologies such as trains, skyships, and mechanical beings which are powered by magic.