Scholars have identified numerous themes in J. R. R. Tolkien's Middle-earth writings, among them paganism. Despite Tolkien's assertion that The Lord of the Rings was a fundamentally Christian work, paganism appears in that book and elsewhere in his fictional world of Middle-earth in multiple ways. These include a pantheon of god-like beings, the Valar, who function like the Norse gods, the Æsir; the person of the wizard Gandalf, who Tolkien stated in a letter is an "Odinic wanderer"; Elbereth, the Elves' "Queen of the Stars", associated with Venus; animism, the way that the natural world seems to be alive; and a Beowulf-like "northern courage" which is determined to press on, no matter how bleak the outlook.

Tolkien was a Christian interested in religion, and placed many hints of Christianity in The Lord of the Rings, but given that Middle-earth is the Earth in the distant past, long before the time of Christ, he could not make his characters Christian, even the most virtuous pagans among them. He was in addition a philologist, a scholar of Old English language and literature, especially of Beowulf, and he made extensive use of that poem in his Middle-earth writings.

Paganism covers an eclectic mix of religious beliefs and practices, often including many gods (polytheism) and a living nature imbued with spirit (animism). It was defined in early Christian times largely negatively, as non-Christian religion. Pagans may speak as if there was just one deity, often "the Goddess", while accepting multiple deities; they may speak of nature or the Earth as divine, suggesting a form of pantheism, though this may shade into either animism or transcendentalism. There is thus a wide spectrum of belief.

J. R. R. Tolkien was a devout Roman Catholic. He described The Lord of the Rings as "fundamentally" Christian, and there are many Christian themes in that work. He wrote in a letter to his close friend and Jesuit priest, Robert Murray:

The Lord of the Rings is of course a fundamentally religious and Catholic work; unconsciously so at first, but consciously in the revision. That is why I have not put in, or have cut out, practically all references to anything like 'religion', to cults or practices, in the imaginary world. For the religious element is absorbed into the story and the symbolism.

The scholar Patrick Curry writes that Tolkien's statement elides the paganism that pervades the work, and indeed the whole of his Middle-earth Legendarium; it may be fundamentally Christian, but on other levels it is another matter, with its pagan polytheism and animism, and many other features. In other words, Middle-earth is both Christian and pagan. Pat Reynolds of the Tolkien Society writes that the Catholic Tolkien was familiar with multiple systems of belief, something that did not in his view imply that Tolkien was "a closet pagan". Reynolds adds that, on the contrary, Tolkien stated explicitly in a letter that The Lord of the Rings "is built on or out of certain 'religious' [Catholic] ideas, but is not an allegory of them ... and does not mention them overtly". The Episcopal priest and theologian Fleming Rutledge adds that Middle-earth deliberately appears as "a curiously nonreligious world", since Tolkien wanted to avoid any hint of pantheism, pagan worship of the natural world.

Professionally, 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 Beowulf, telling of a pagan world but with a Christian narrator, helped to shape his fictional world of Middle-earth. His intention to create what has been called "a mythology for England" led him to construct not only stories but a fully-formed world with languages, peoples, cultures, and history, based on medieval materials.

Middle-earth is part of the created world, Eä, ruled by "the One" god, Eru Iluvatar, who in Tolkien's words "remains remote, outside the World", making it in principle monotheistic and thus compatible with Christianity. In practice, Middle-earth is ruled by a pantheon-like group of “angelic-beings”, the Valar, who function, as Tolkien stated, with "the imaginative but not the theological place of 'gods'". They are, further, related to the four ancient elements of fire, earth, air, and water in a characteristically pagan way. This makes Middle-earth appear polytheistic. Among the resemblances are the strong Oromë who fights the monsters of Melkor, recalling the powerful Norse god Thor.