The Complete Guide to Middle-earth: from The Hobbit to The Silmarillion is a reference book for J. R. R. Tolkien's fictional universe of Middle-earth, compiled and edited by Robert Foster. It was first published in 1971 under the title A Guide to Middle-earth. A revised and enlarged edition under the title The Complete Guide to Middle-earth was published in 1978. It received a third edition in 2001.

Middle-earth is the setting of much of the English writer J. R. R. Tolkien's fantasy. The term is equivalent to the Miðgarðr of Norse mythology and Middangeard in Old English works, including Beowulf. Middle-earth is the human-inhabited world, that is, the central continent of the Earth, in Tolkien's imagined mythological past. Tolkien's most widely read works, The Hobbit and The Lord of the Rings, are set entirely in Middle-earth. "Middle-earth" has also become a short-hand term for Tolkien's legendarium, his large body of fantasy writings, and for the entirety of his fictional world.