A Guide to Middle-earth was the first published encyclopedic reference book for the fictional universe of J. R. R. Tolkien's Middle-earth, compiled and edited by Robert Foster. The book was published in 1971 by Mirage Press, a specialist science fiction and fantasy publisher, in a limited edition of 2000 copies (750 numbered hardcovers and 1250 unnumbered paperbacks). A paperback edition was issued by Ballantine Books in 1974.
The author profile on the first edition describes Robert Foster as the then-"Tengwar Consultant" to the Tolkien Society of America, and the book incorporates material previously published in the science fiction fanzine Niekas.
A much-expanded edition incorporating entries for The Silmarillion was issued in 1978 by Ballantine under the title The Complete Guide to Middle-earth, and a further revised edition (ISBN 0-345-44976-2) was published in 2001 in time for The Lord of the Rings film trilogy.
Lester del Rey praised the 1971 version for covering "literally everything you wanted to know about Middle Earth and were unable to discover before."