Low fantasy is a sub-genre of fantasy fiction involving "nonrational happenings that are without causality or rationality because they occur in the rational world where such things are not supposed to occur." Low fantasy stories are set either in the real world or a fictional but rational world, and are contrasted with high fantasy stories which take place in a completely fictional fantasy world setting with its own set of rules and physical laws.

Low fantasy places relatively less emphasis on typical elements associated with fantasy, setting a narrative in real-world environments with elements of the fantastical. Sometimes there are just enough fantastical elements to make ambiguous the boundary between what is real and what is purely psychological or supernatural. The word "low" refers to the level of prominence of traditional fantasy elements within the work, and is not any sort of remark on the works' quality.