- Orozco, Daniel (1957- ) (stories)
- See en.wikipedia.org/wiki/Daniel_Orozco
- Orpaz, Yitzhak (1921-2015) (stories)
- See en.wikipedia.org/wiki/Yitzhak_Orpaz
- Orpen, Adela E(lizabeth Richards) (1855-1927) (stories)
- Born in Virginia; died in Ireland.
- Orpen, [Major Sir] William (Newenham Montague) (1878-1931) (stories) (art) (assoc.)
- See en.wikipedia.org/wiki/William_Orpen
- Orr, Clifford (Burrowes) (1899-1951) (stories)
- Born in Maine, graduate of Dartmouth; editor of The New Yorker.
- Orringer, Julie (1973- ) (stories)
- See en.wikipedia.org/wiki/Julie_Orringer
- Orrmont, Arthur (1922-2007) (stories)
- See prabook.com/web/arthur.orrmont/357060
- Orsborne, Dod (fl. 1950s) (stories)
- Explorer, adventurer, sailor, writer. Born in Dundee, Scotland; died in Belle-Isle, France.
- Orsi, Carlos [i.e., Carlos Orsi Martinho] (1971- ) (stories)
- See pt.wikipedia.org/wiki/Carlos_Orsi_Martinho
- Ortega y Gasset, José (1883-1955) (stories)
- See en.wikipedia.org/wiki/José_Ortega_y_Gasset
- Ortega, Francisco (1974- ) (stories)
- See en.wikipedia.org/wiki/Francisco_Ortega_(writer)
- Ortiz, Karla ({c}1985- ) (art)
- See karlaortizart.blogspot.co.uk
- Ortlieb, Marc (fl. 1970s-1990s) (stories) (assoc.)
- See fancyclopedia.org/marc-ortlieb
- Orullian, Peter (1969- ) (stories) (assoc.)
- See en.wikipedia.org/wiki/Peter_Orullian
- Orville, Howard T(homas) (1901-1960) (stories)
- See en.wikipedia.org/wiki/Howard_Thomas_Orville
- Orwell, George; pseudonym of Eric Blair (1903-1950) (stories) (assoc.)
- See en.wikipedia.org/wiki/George_Orwell
- Osborn, Harold M(arion) (1899-1975) (stories) (assoc.)
- See en.wikipedia.org/wiki/Harold_Osborn
- Osborn, Marijane (fl. 1980s-2010s) (stories)
- See english.ucdavis.edu/people/directory/ansuz
- Osborn, Stanley R. (1876-1946) (stories)
- A journalist, born in Nebraska.
- Osborne, Beverly (fl. 1930s-1950s) (stories) (assoc.)
- See chickenintherough.com/History.html
- Osborne, Cary G. (fl. 1980s-2010s) (stories)
- See iroshioftheglaive.blogspot.co.uk
- Osborne, Charles (Thomas) (1927-2017) (stories)
- See en.wikipedia.org/wiki/Charles_Osborne_(music_writer)
- Osborne, (Samuel) Duffield (1858-1917) (stories)
- See www.sf-encyclopedia.com/entry/osborne_duffield
- Osborne, Emily (fl. 2010s) (stories) (art)
- See emko.carbonmade.com
- Osborne, Emma (K.) (fl. 2010s) (stories) (assoc.)
- See emmakosborne.com
- Osborne, Ernest (1878-1954) (stories)
- Miner, planter and journalist; born in Wallsend, New South Wales.
- Osborne, J. David (fl. 2010s) (stories)
- See www.brokenriverbooks.com
- Osborne, John (James) (1929-1994) (stories) (assoc.)
- See en.wikipedia.org/wiki/John_Osborne
- Osborne, Lawrence (1958- ) (stories) (assoc.)
- See en.wikipedia.org/wiki/Lawrence_Osborne
- Osborne, Rubye (fl. 1930s-1950s) (stories) (assoc.)
- See chickenintherough.com/History.html
- Osborne, Stephanie (fl. 2010s) (stories)
- See www.sff.net/people/steph-osborn
- Osborne, William Hamilton (1873-1942) (stories)
- See www.jerseyhistory.org/findingaid.php?aid=1137
- Osbourne, Lloyd (1868-1947) (stories)
- See www.sf-encyclopedia.com/entry/osbourne_lloyd
- Oscar II of Sweden and Norway, King (1829-1907) (stories) (assoc.)
- See en.wikipedia.org/wiki/Oscar_II_of_Sweden
- Osgood, Irene ({c}1869-1922) (stories)
- Born Irene De Belot near Richmond, Virginia; married someone named Osgood, then Charles Piggot Harvey, then Robert Sherard.
- Osgood, Kate Putnam (1841-1910) (stories)
- See en.wikisource.org/wiki/Author:Kate_Putnam_Osgood
- OShaughnessy, Arthur W(illiam Edgar) (1844-1881) (stories)
- See en.wikipedia.org/wiki/Arthur_O%27Shaughnessy
- OSheel, Shaemas [born James Shields] (1886-1954) (stories)
- See en.wikipedia.org/wiki/Shaemas_OSheel
- Oshiro, Mark (fl. 2010s) (stories)
- See markdoesstuff.tumblr.com
- Osias, Kate (Aton) (fl. 2000s-2010s) (stories)
- See wishcatcher.blogspot.co.uk
- Osler, [Sir] William (1849-1919) (stories) (assoc.)
- See en.wikipedia.org/wiki/William_Osler
- Osmond, Marion (Wallace) (1870-1948) (stories)
- Born Marion Wallace in London; married Walter Osmond, one time special constable at Buckingham Palace; died in London.
- Östberg, Jeff (fl. 2010s) (art)
- See jeffostberg.se
- Ostby, Gertrude Enid (1920-2012) (stories)
- See www.anewtradition.com/obituaries/obituary/5133_Gertrude_Enid_Ostby
- Ostenso, Martha (1900-1963) (stories) (assoc.)
- See en.wikipedia.org/wiki/Martha_Ostenso
- Oster, Jerry (1943- ) (stories)
- Possibly a pseudonym.
- Ostlere, Gordon Stanley (1921-2017) (stories)
- See en.wikipedia.org/wiki/Richard_Gordon_(English_author)
- Ostow, Micol (1976- ) (stories)
- See en.wikipedia.org/wiki/Micol_Ostow
- Ostrander, Isabel [i.e., Isabella Egenton Ostrander Lamb] (1883-1924) (stories) (assoc.)
- Born in New York City.
- Ostrovski, Emil (fl. 2010s) (stories)
- See www.emilostrovski.com
- Ostrovsky, Andrew (fl. 2010s) (art)
- See agsandrew.deviantart.com
- OSullivan, Patrick (fl. 2010s) (stories)
- See patrickcosullivan.com
- OSullivan, Vincent (1868-1940) (stories) (assoc.)
- See modjourn.org/render.php?view=mjp_object&id=mjp.2005.01.028
- OSullivan, Vincent (Gerard) (1937- ) (stories)
- See en.wikipedia.org/wiki/Vincent_OSullivan_(New_Zealand_poet)
- OSullivan, William (fl. 1900s-1960s) (stories) (assoc.)
- probably a house pseudonym.
- Oswald, Felix L(eopold) (1845-1906) (stories) (art)
- See en.wikipedia.org/wiki/Felix_Leopold_Oswald
- Oswald, James (fl. 2010s) (stories)
- See jamesoswald.co.uk
- Oswald, Lee Harvey (1939-1963) (stories) (assoc.)
- See en.wikipedia.org/wiki/Lee_Harvey_Oswald
- Oswalt, (Peter) Patton (1969- ) (stories)
- See en.wikipedia.org/wiki/Patton_Oswalt
- Otis, Abbey Mei (fl. 2010s) (stories)
- See www.goodreads.com/author/show/5456552.Abbey_Mei_Otis
- Otis, Alexander (1867-1939) (stories)
- Born in Dover, Massachusetts; a lawyer.
- Otis, Elita Proctor (1851-1927) (stories)
- See en.wikipedia.org/wiki/Elita_Proctor_Otis
- Otis, James; pseudonym of James Otis Kaler (1848-1912) (stories)
- See www.sf-encyclopedia.com/entry/otis_james
- OToole, George J. (1936-2001) (stories)
- See www.sf-encyclopedia.com/entry/otoole_george
- Otsuka, Julie (1962- ) (stories)
- See en.wikipedia.org/wiki/Julie_Otsuka
- Ott, Anthony B. (fl. 1940s-1950s) (stories)
- possibly a pseudonym.
- Ott, [Dr.] John N(ash) (1909-2000) (stories) (assoc.)
- See en.wikipedia.org/wiki/John_Ott
- Ott, Mel(vin Thomas) (1909-1958) (stories)
- See en.wikipedia.org/wiki/Mel_Ott
- Ottaviani, Jim (1963- ) (stories)
- See en.wikipedia.org/wiki/Jim_Ottaviani
- Otto, Whitney (1955- ) (stories)
- See en.wikipedia.org/wiki/Whitney_Otto
- Ottolengui, (Benjamin A.) Rodrigues (1861-1937) (stories) (assoc.)
- See www.sf-encyclopedia.com/entry/ottolengui_rodrigues
- Otus, Erol (fl. 1970s-2010s) (stories) (assoc.)
- See en.wikipedia.org/wiki/Erol_Otus
- Otway, Leslie (fl. 1920s-1930s) (art)
- See bearalley.blogspot.com/2007/01/leslie-otway.html
- Ouellette, Pierre (1945- ) (stories) (assoc.)
- See www.sf-encyclopedia.com/entry/ouellette_pierre
- Ouida; pseudonym of Maria Louise Ramé (1839-1908) (stories) (assoc.)
- See en.wikipedia.org/wiki/Ouida
- Oulahan, Richard (1867-1931) (stories)
- Journalist, well known correspondent. Born and died in Washington, D.C.
- Ould, Chris (1959?- ) (stories) (assoc.)
- See www.sf-encyclopedia.com/entry/ould_chris
- Oulton, Carolyn (W. de la L.) (1972- ) (stories) (assoc.)
- See www.canterbury.ac.uk/arts-and-humanities/school-of-humanities/Staff/Profile.aspx?staff=9a28ec2232ccc5df
- Oursler, Grace (Perkins) (1900-1955) (stories)
- Born in Boston; educated at Columbia School of Journalism.
- Ouse, David (fl. 2010s) (stories)
- See zenithcity.com/author/davo
- Outfield, Rish (fl. 2010s) (stories)
- See rishoutfield.blogspot.co.uk
- Outhwaite, Ida Rentoul (1888-1960) (stories) (assoc.)
- See en.wikipedia.org/wiki/Ida_Rentoul_Outhwaite
- Overend, W(illiam) H(eysman) (1851-1898) (art)
- See bearalley.blogspot.com/2018/08/w-h-overend.html
- Overholser, Stephen (1944- ) (stories)
- See www.sf-encyclopedia.com/entry/overholser_stephen
- Overholser, Wayne D. (1906-1996) (stories) (assoc.)
- See en.wikipedia.org/wiki/Wayne_D._Overholser
- Overman, Beulah Rhodes (1894-1990) (stories)
- See newsok.com/beulah-rhodes-overman/article/2340740
- Overton, J(ohn) H(enry) (1835-1903) (stories)
- See en.wikipedia.org/wiki/John_Henry_Overton
- Overton, John Henry (1835-1903) (stories)
- See en.wikipedia.org/wiki/John_Henry_Overton
- Overton, Robert (1854-1924) (stories)
- Author, playwright, journalist, lecturer on literature and philosophy, and writer of monologues, pantomimes and operettas.
- Øvstedal, Barbara Kathleen (1921-2012) (stories)
- Born Barbara Skathleen Geils in Sussex; married Inge Øvstedal in 1945.
- Ow, Anya (fl. 2010s) (stories) (assoc.)
- See anyasy.com
- Owbridge, Eileen [born Eileen Norah Murphy] (1903-1994) (stories)
- See bearalley.blogspot.co.uk/2017/05/eileen-owbridge.html
- Owen, (Harry) Collinson (1882-1956) (stories)
- See en.wikipedia.org/wiki/Harry_Collinson_Owen
- Owen, David (Donald) (1956- ) (stories) (assoc.)
- See tasmanianartsguide.com.au/artists/writers/david-owen/
- Owen, Dean; pseudonym of Dudley Dean McGaughey (1909-1986) (stories)
- See www.sf-encyclopedia.com/entry/owen_dean
- Owen, Frank (1893-1968) (stories) (art) (assoc.)
- See tellersofweirdtales.blogspot.co.uk/2015/06/frank-owen-1893-1968.html
- Owen, H(arry) Collinson (1882-1956) (stories)
- Journalist and author.
- Owen, James A. (fl. 1970s-2010s) (stories) (art)
- See jamesaowen.com/
- Owen, Jule (fl. 2010s) (stories)
- See juleowen.com
- Owen, Mickey [i.e., Arnold Malcolm Owen] (1916-2005) (stories) (assoc.)
- See en.wikipedia.org/wiki/Mickey_Owen