Although fantasy had long existed in various forms around the world before his time, J. R. R. Tolkien has been called the "father of fantasy", and The Lord of the Rings its centre. That novel, published in 1954–1955, enormously influenced fantasy writing, establishing in particular the form of high or epic fantasy, set in a secondary or fantasy world in an act of mythopoeia. The book was distinctive at the time for its considerable length, its "epic" feel with a cast of heroic characters, its wide geography, and its battles. It involved an extensive history behind the action, an impression of depth, multiple sentient races and monsters, and powerful talismans. The story is a quest, with multiple subplots. The novel's success demonstrated that the genre was commercially distinct and viable.

Many later fantasy writers have either imitated Tolkien's work, or have written in reaction against it. One of the first was Ursula Le Guin's Earthsea series of novels, starting in 1968, which used Tolkienian archetypes such as wizards, a disinherited prince, a magical ring, a quest, and dragons. A publishing rush followed. Fantasy authors including Stephen R. Donaldson and Philip Pullman have created intentionally non-Tolkienian fantasies, Donaldson with an unloveable protagonist, and Pullman, who is critical of The Lord of the Rings, with a different view of the purpose of life.

The genre has spread into film, into both role-playing and video games, and into fantasy art. Peter Jackson's 2001–2003 The Lord of the Rings film series brought a new and very large audience to Tolkien's work. Tolkien's influence reached role-playing games as early as 1974 with Gary Gygax's Dungeons & Dragons; this was followed by many Middle-earth video games, some directly licensed and others based on Tolkienian fantasy culture. Tolkien's fantasies have been illustrated by artists such as John Howe, Alan Lee, and Ted Nasmith, who have become known as "Tolkien artists".

J. R. R. Tolkien was a scholar of English literature, a philologist and medievalist interested in language and poetry from the Middle Ages, especially that of Anglo-Saxon England and Northern Europe. His professional knowledge of works such as Beowulf shaped his fictional world of Middle-earth, including his high fantasy novel The Lord of the Rings. This did not prevent him from making use of modern sources including fantasy as well; the J.R.R. Tolkien Encyclopedia discusses 25 authors whose works are paralleled by elements in Tolkien's writings.

The Lord of the Rings was constructed with several distinctive features. These included its considerable length, remarkable for its time when few genre novels exceeded 65,000 words. This was accompanied by an "epic" feel, created by a combination of features such as its cast of heroic characters, its wide geography, and its battles. The story is told with allusions to older times, giving both an impression of depth behind the action, and a past that fades into mythology. The heroes encounter multiple sentient races, including both free peoples like elves and dwarves, and monsters like trolls and giant spiders. Powerful talismans are deployed, such as swords with their own names, wizards' staffs, magical rings and seeing stones. As for the story, there is a quest, accompanied by many subplots. As if this were not enough, Tolkien gives the plot a moral dimension: the characters have to rely on their own courage and luck, believing that the unseen powers will support them.

The Lord of the Rings, and to some extent also his 1937 children's novel, The Hobbit, make use of multiple elements to make the fantasy world of Middle-earth convincing. These include detailed maps with a large number of placenames; an impression of depth; a frame story; poetry interspersed with the narrative; family trees; invented languages that had been worked out in detail, complete with scripts; artwork; and heraldry.

The impression of depth in particular helps to make Middle-earth feel like what Tom Shippey has called "a coherent, consistent, deeply fascinating world about which [Tolkien] had no time [then] to speak". As another example, the heraldry helps to convey impressions such as the "evident majesty" of the hero Aragorn:

upon the foremost ship a great standard broke, and the wind displayed it as she turned towards the Harlond. There flowered a White Tree, and that was for Gondor; but Seven Stars were about it, and a high crown above it, the signs of Elendil that no lord had borne for years beyond count. And the stars flamed in the sunlight, for they were wrought of gems by Arwen daughter of Elrond; and the crown was bright in the morning, for it was wrought of mithril and gold.