Thomas Keightley (17 October 1789 – 4 November 1872) was an Irish writer known for his works on mythology and folklore, particularly Fairy Mythology (1828), reprinted as The World Guide to Gnomes, Fairies, Elves, and Other Little People (1880, 1978, 2000, etc.).
Regarded as a pioneer in the study of Folklore by modern scholars in the field, he was one of the "early and important comparativist collectors" of folklore.
A circumspect scholar, he did not deem that similar tales recognizable across countries automatically signified transmission, but allowed that similar tales could arise independently in different cultures.
At the request of the educator Thomas Arnold, he authored a series of textbooks on English, Greek, and other histories, which were adopted at Arnold's Rugby School as well as other public schools.