Mythopoeia (also mythopoesis, after Hellenistic Greek μυθοποιία, μυθοποίησις "myth-making") is a narrative genre in modern literature and film where a fictional mythology is created by the writer of prose or other fiction. This meaning of the word mythopoeia follows its use by J. R. R. Tolkien in the 1930s. The authors in this genre integrate traditional mythological themes and archetypes into fiction.

Mythopoeia is also the act of making (creating) mythologies. Notable mythopoeic authors include Tolkien, C. S. Lewis, William Blake, H. P. Lovecraft, Lord Dunsany, Mervyn Peake and George MacDonald. While many literary works carry mythic themes, only a few approach the dense self-referentiality and purpose of mythopoeia. It is invented mythology that, rather than arising out of centuries of oral tradition, are penned over a short period of time by a single author or small group of collaborators.

As distinguished from fantasy worlds or fictional universes aimed at the evocation of detailed worlds with well-ordered histories, geographies, and laws of nature, mythopoeia aims at imitating and including real-world mythology, specifically created to bring mythology to modern readers, and/or to add credibility and literary depth to fictional worlds in fantasy or science fiction books and movies.

Genre ( /ˈʒɒnrə/ or /ˈdʒɒnrə/; from French, genre French pronunciation: [ʒɑ̃ʁ], "kind" or "sort", from Latin: genus (stem gener-), Greek: genos, γένος) is the term for any category of literature or other forms of art or entertainment, e.g. music, whether written or spoken, audial or visual, based on some set of stylistic criteria. Genres are formed by conventions that change over time as new genres are invented and the use of old ones are discontinued. Often, works fit into multiple genres by way of borrowing and recombining these conventions.

The concept of genre originated from the classification systems created by Aristotle and Plato. Plato divided literature into the three classic genres accepted in Ancient Greece: poetry, drama, and prose. Poetry is further subdivided into epic, lyric, and drama. The divisions are recognized as being set by Aristotle and Plato; however, they were not alone. Many genre theorists contributed to these universally accepted forms of poetry. Similarly many theorists continued to philosophize about genre and its uses, which caused genre as Plato and Aristotle knew it to evolve and further expand.