======Essays======
- King Lear (1934)
- The Works of H.P. Lovecraft: Suggestions for a Critical Appraisal (1944)
- Some Random Thoughts About Lovecraft's Writings (1945)
- Leiber on Onderdonk (1945)
- Letter (The Acolyte, Fall 1945) (1945)
- Foreword (Night's Black Agents) (1947)
- Fantasy on the March (1948)
aka A Defense of Werewolves (1948)
- A Literary Copernicus (1949)
- Debunking the I Machine (1949)
- A Contrasting Duo (1949)
- From the Fan Presses (1949)
- Should Population Be Controlled? Yes (1951)
- Hottest and Coldest Molecules (1952)
- Icon of the Imagination (1954)
- Snaring the Human Mind (1954)
- My Correspondence with Lovecraft (1958)
- John Carter: Sword of Theosophy (1959)
- Weird World of the Knight (1960)
- Foreword (The Mind Spider and Other Stories) (1961)
- Howard's Style (1961)
aka Robert E. Howard's Style (1961)
- The Mighty Tides (1961)
- Fafhrd and Me (1963)
- Lovecraft: A Symposium (1963) with Leland Sapiro and Arthur J. Cox
- Through Hyperspace with Brown Jenkin (1963)
aka Through Hyperspace with Brown Jenkin: Lovecraft's Contribution to Speculative Fiction (1966)
- "The Whisperer" Re-examined (1964)
- Monsters and Monster Lovers (1965)
- Guest Editorial: Monsters & Monster-Lovers (1965)
- Letter (Zenith Speculation, October 1965) (1965)
- Controlled Anachronism (1966)
- Titivated Romance (1966)
- The Anima Archetype in Science Fiction (1967)
- Introduction (A Glass of Stars) (1968)
- Author's Foreword (The Swords of Lankhmar) (1968)
- Author's Note (The Swords of Lankhmar) (1968)
- Comments on Myths My Great-Granddaughter Taught Me (1968)
- Letter (Speculation 21) (1969)
- Awareness of Mortality (1969)
- Fantasy Books (Fantastic, February 1970) (1970) with Alexander Temple
- Fantasy: Many Mansions and Hovels (1971)
- Author's Introduction (Swords Against Death) (1973)
- Author's Foreword (Swords and Deviltry) (1973)
- Introduction (Swords and Deviltry) (1973)
- Author's New Introduction (Swords Against Death) (1973)
- Author's Foreword (Swords Against Death) (1973)
- J. R. R. Tolkien [appreciation] (1973)
- Author's Introduction (Swords Against Wizardry) (1973)
- Author's Introduction (Swords and Deviltry) (1973)
- Those Wild Alien Words: I (1974)
- Afterword (The Best of Fritz Leiber) (1974)
- Foreword (The Book of Fritz Leiber) (1974)
- Introduction (The Best of Fritz Leiber) (1974)
- After Such Knowledge (1974)
- Masters of Mace and Magic (1974)
- Fantasy and SF Films (Media Review) (1974)
- Ingmar Bergman: Fantasy Novelist (1974)
- New Fantasy Films (Media Review) (1974)
- The Cthulhu Mythos: Wondrous and Terrible (1975)
- Those Wild Alien Words: II (1975)
- Foreword (The Second Book of Fritz Leiber) (1975)
- Introduction (The Worlds of Fritz Leiber) (1976)
- Lovecraft in My Life (1976)
- Fafhrd & The Mouser Say Their Say (1976)
- Wonder and Terror (1976)
- Time and Nth Dimension (1977)
- Introduction to Fafhrd and the Gray Mouser (1977)
- Author's Foreword (Lean Times in Lankhmar) (1977)
- Author's Foreword (Swords in the Mist) (1977)
- Introduction (Swords Against Wizardry) (1977)
- Author's Foreword (Swords Against Wizardry) (1977)
- Introduction: Birthpangs of Hyboria (1978)
- Introduction (Bazaar of the Bizarre) (1978)
- Letter #1 (Science Fiction Review #24) (1978)
- Letter #2 (Science Fiction Review #24) (1978)
- Afterword (Riding the Torch) (1978)
- Introduction (The Childhood and Youth of the Gray Mouser) (1978)
- Introduction: Wonder and Terror (1979)
- "When Screwballs Meet..." (1979)
- Fantasy Books (Locus #218) (1979)
- About "The Automatic Pistol" (1979)
- Enzenbacher's Eight Norse Gods (1979)
- The Change War Series (1980)
- Introduction: Terror, Mystery, Wonder (1980)
- Author's Afterword (The Sinful Ones) (1980
- Afterword (The Sinful Ones) (1980)
- Rooftop Astronomy or A Writer's Dark Side (1981)
- Author's Foreword (Swords and Ice Magic) (1981)
- Fantasy Books: More Notes After Reading Danse Macabre (1981)
- The Orycon 80 Convention Four-Way Telephone Conversation (1981) with Arthur C. Clarke and Harlan Ellison and Mark Wells
- By Another Hand . . . (Locus #248) (1981)
- Letter (Science Fiction Review #41) (1981)
- Introduction (The Big Time) (1982)
- Horror Hits a High (1982)
- The Mystery of the Japanese Clock (1982)
- Why is the Horror Genre Frowned Upon by the Literary Establishment? (1982)
- The Glory of Tros (1983)
- My Life and Writings, Part 4: Midlife Crossroads (1983)
- Obituary: James Wade (1983)
- Howard's Fantasy (1984)
- My Life & Writings, Part 5: A Living from Writing? Sober on the Coast! (1984)
- Author's Introduction (The Ghost Light) (1984)
- Not Much Disorder and Not So Early Sex: An Autobiographic Essay (1984)
- My Life & Writings, Part 6: Ups & Downs; Return to Alcohol (1984)
- My Life & Writings, Part 7: Business, Bereavement, Flight (1984)
- My Life & Writings, Part 8 - Conclusion: San Francisco: New Beginnings (1984)
- The Changing Face of Horror (1984)
- Letter (Fantasy Review, December 1984) (1984)
- The Profession of SF: Mysterious Islands (1984)
- Letter (Fantasy Review, March 1985) (1985)
- Obituary: Harry Otto Fischer (1986)
- Mise au Point (Epées et Sorciers) (1986)
- Author's Note (Black Corridor) (1988)
- Author's Introduction (Swords and Deviltry (1989)
- Response to "The New Generation Gap" (1989)
- Author's Foreword (?) (1990)
- Review of "The Knight, Death, and the Devil" by Ella Leffland (1990)
- My Life and Writings (1990)
- Review of "The Magic Lantern: An Autobiography" by Ingmar Bergman (1991)
- Obituary: Martha ""McElroy"" Fischer (1991)
- The Grail Legend: An Introduction (Grails: Quests, Visitations and Other Occurrences) (1992)
- H. P. Lovecraft Meets Fafhrd and The Gray Mouser (1992)
- The Grail Legend: An Afterword (Grails: Quests of the Dawn) (1992)
- Introduction (Gummitch and Friends) (1992)
- Fritz Leiber: Selected Letters to Franklin ""MacKnight"", 1945-1951 (Part 1) (1998)
- Fritz Leiber: Selected Letters to Franklin ""MacKnight"", 1945-1951 (Part 2) (1998)
- Introduction (Lankhmar: Tales of Fafhrd and the Gray Mouser) (2000)