Avram Davidson (April 23, 1923 May 8, 1993) was an American writer of SF and crime fiction, prolific and award-winning in both fields.

Probably his best-known story is the UsefulNotes/HugoAward-winning "Or All the Seas With Oysters", which posits a creative unified theory to explain a set of everyday questions beginning with 'Why is there never a paperclip to be found when I need one?'.

Several of his notable SF works feature history that never quite was, such as in his stories featuring Dr Eszterhazy, a respected scientist in the 19th-century {{Ruritania}}n empire of Scythia-Pannonia-Transbalkania, or the Vergil Magus series, beginning with ''The Phoenix and the Mirror'', which is set in the Roman empire not as it was but as people of the Middle Ages imagined it to be.

Two of his crime fiction stories, "The Ikon of Elijah" (in which an antique dealer goes to extreme lengths to obtain a valuable antique) and "Thou Still Unravished Bride" (in which a woman goes missing on her wedding day) were adapted for episodes of ''Series/AlfredHitchcockPresents''.
!!Avram Davidson's works provide examples of:

* TheButlerDidIt: One story features the writer who invented the trope, and a large number of disgruntled butlers.
* ChineseLaunderer: The title character of "The Deed of the Deft-Footed Dragon"
* ForWantOfANail:
** In "O Brave Old World!", a small change results in the American Revolution being the occasion on which ''England'' revolted against the rule of ''America''.
** In "Pebble in Time", a time traveller dislodges a single pebble and causes a massive change to the history of the western United States.
* GeniusBonus: Ubiquitous in Davidson's work
* GoingToSeeTheElephant: "The Man Who Saw the Elephant"
* HeAlsoDid: The foreword to one collection of Davidson's stories notes that people who are mostly familiar with his crime fiction often have this reaction to the discovery that he wrote SF, and vice versa. Among other things he ghost-wrote a few of the later Literature/ElleryQueen books, when Dannay & Lee had reduced their input to plotting.
* HistoricalDomainCharacter: In several of his historical-set stories.
* LiteraryAllusionTitle:
** "Thou Still Unravished Bride" is a quotation from Creator/JohnKeats.
** "O Brave Old World!" is a misquotation of a line from ''Theatre/TheTempest''.
* MockMillionaire: The title character of "Captain Pasharooney" turns out to be one of these, though with an unselfish motivation.
* OmnidisciplinaryScientist: Dr Esterhazy -- sometimes addressed as ''Drs'' Esterhazy, on account of possessing doctorates in more than one field.
* PosthumousCollaboration: ''The Boss in the Wall'', completed by his wife, Grania Davis
* {{Pride}}: The aliens lure Doctor Morris Goldpepper into slavery by playing to his vanity and pretending to offer him the chance to be a groundbreaker on their world too.
* PublicDomainCharacter: The [[Literature/SherlockHolmes English doctor and his disconcertingly-observant friend]], both unnamed, in "The Singular Incident of the Dog on the Beach"
* {{Ruritania}}: Scythia-Pannonia-Transbalkania
* SiblingTriangle: In "The Cobblestones of Saratoga Street", two sisters discover that they've fallen in love with the same man, who has been seeing each behind the other's back.
* TimeTravel: In "Pebble in Time", a man invents a time machine and uses it to go and watch his favourite historical moment. Despite taking great care to keep out of the way, he inevitably (since there'd be no story otherwise) manages to make a mess of it.
* TheWoobie: Dr. Morris Goldpepper.