- Oemler, Marie Conway (1879-1932) (stories)
- Born in Savannah, Georgia; contributed poems and short stories to magazines.
- OFaoláin, Seán (Proinsias) [born John Francis Whelan] (1900-1991) (stories)
- See en.wikipedia.org/wiki/Se%C3%A1n_%C3%93_Faol%C3%A1in
- OFarrell, Brigid (fl. 1930s) (stories)
- Name also given as Brigid OFarrel.
- Offor, Beatrice (1864-1920) (art)
- See beatriceoffor.com.au
- Offutt, Andrew J(efferson, V) (1934-2013) (stories) (assoc.)
- See www.sf-encyclopedia.com/entry/offutt_andrew_j
- OFlaherty, Liam (1896-1984) (stories) (assoc.)
- See en.wikipedia.org/wiki/Liam_O%27Flaherty
- Oga, Takeshi (fl. 2010s) (art)
- See www.takeshioga.com
- Ogan, George (F.) (1912-1983) (stories)
- Writer and teacher. Born in Kirkwood, Missouri; lived in Louisiana.
- Ogan, Margaret (E. Nettles) (1923-1979) (stories)
- Teacher and writer, born in Columbia, Louisiana.
- Ogas, Ogi (Jonathan) (1971- ) (stories) (assoc.)
- See en.wikipedia.org/wiki/Ogi_Ogas
- Ogburn, Charlton, Jr. (1911-1998) (stories)
- See en.wikipedia.org/wiki/Charlton_Ogburn
- Ogden, G(eorge) W(ashington) (1871-1966) (stories) (assoc.)
- Born in Kansas, died in Los Angeles; a newspaperman who became a prolific author of westerns in later life.
- Ogilvie, Elisabeth (May) (1917-2006) (stories)
- See en.wikipedia.org/wiki/Elisabeth_Ogilvie
- Ogilvie, Frances [i.e., Frances Ogilvie Nichols] (1902-1942) (stories)
- Born in Princeton, Kentucky; married Earle M. Nichols in 1937; some sources give her birth as 1903.
- Ogilvie, Will(iam) H(enry) (1869-1963) (stories)
- See en.wikipedia.org/wiki/William_Henry_Ogilvie
- Ogle, Richard B(ertram) (1889-1976) (stories) (art)
- See bearalley.blogspot.co.uk/2008/09/richard-ogle.html
- Oglesby, W(illiam) H. Ellis (1966- ) (stories)
- Freelance writer in Atlanta, Georgia.
- Oglethorpe, [General] James Edward (1696-1785) (stories) (assoc.)
- See en.wikipedia.org/wiki/James_Oglethorpe
- OGorman, (Maria) Camila ({c}1827-1848) (stories) (assoc.)
- See en.wikipedia.org/wiki/Camila_O%27Gorman
- OGrady, Standish James (1846-1928) (stories)
- See www.sf-encyclopedia.com/entry/ogrady_standish_james
- Ogurek, Douglas J. (fl. 2010s) (stories) (assoc.)
- See douglasjogurek.weebly.com
- Ogutsch, Edith (1929-1990) (stories)
- See tellersofweirdtales.blogspot.co.uk/2016/01/edith-ogutsch-1929-1990.html
- Oh, Susie (fl. 2010s) (stories) (art) (assoc.)
- See susieoh.net
- Oh, Temi (fl. 2010s) (stories) (assoc.)
- See www.theonlytemioh.com
- OHagan, Anne (1869-1933) (stories)
- See en.wikipedia.org/wiki/Anne_O%27Hagan_Shinn
- OHagan, Howard (1902-1982) (stories) (assoc.)
- Reporter, journalist, publicist. Born in Lethbridge, Alberta, Canada.
- OHanlon, Alice (1840-?) (stories)
- Born in Chorley, Lancashire, England; death not traced.
- OHanlon, James (Francis) (1910-1969) (stories)
- Born in Coney Island, New York; died in Glendale, California; came to Los Angeles in 1931 and appeared in motion pictures as a dancer; then became a screenwriter for films and television.
- OHara, Frank Hurburt (1888-1965) (stories)
- See www.lib.uchicago.edu/e/scrc/findingaids/view.php?eadid=ICU.SPCL.HURBURTOHARA
- OHara, Joseph P. (1895-1975) (stories)
- See en.wikipedia.org/wiki/Joseph_P._O%27Hara
- OHara, Mary [i.e., Mary OHara Alsop] (1885-1980) (stories)
- See en.wikipedia.org/wiki/Mary_OHara_(author)
- OHarra, Jack (fl. 1950s-1960s) (stories)
- Probably a pseudonym.
- OHiggins, Harvey J(errold) (1876-1929) (stories) (assoc.)
- Born in London, Ontario; educated at Toronto University; playwright and author.
- Ohlson, (Douglas) Hereward (1907-1955) (stories) (assoc.)
- See www.sf-encyclopedia.com/entry/ohlson_hereward
- Ohnaka, Kathryn (fl. 2010s) (stories)
- See www.kathrynohnaka.com
- Ohnefalsch-Richter, Max (1850-1917) (stories)
- See www.britishmuseum.org/research/search_the_collection_database/term_details.aspx?bioId=95543
- Ohrt, Wallace L. (fl. 1950s) (stories)
- Born in Saskatchewan, Canada.
- Ojala, Eiko (fl. 2010s) (art)
- See ploom.tv
- Okakura Kakuzō (1862-1913) (stories)
- See en.wikipedia.org/wiki/Okakura_Kakuz%C5%8D
- OKeefe, Claudia (Diane) (1958- ) (stories) (assoc.)
- See www.sf-encyclopedia.com/entry/okeefe_claudia
- OKeefe, Megan E. (fl. 2010s) (stories)
- See meganokeefe.com
- OKeefe, Rose (fl. 2010s) (stories)
- See litreactor.com/team/rose-okeefe
- OKeeffe, Neil (1893-1968) (art)
- Name also given as Neil OKeefe. Born in Creston, Iowa.
- Okorafor, Nnedi(mma Nkemdili) (1974- ) (stories) (assoc.)
- See en.wikipedia.org/wiki/Nnedi_Okorafor
- [Marquess] Ōkuma Shigenobu [born Hachitarō] (1838-1922) (stories) (assoc.)
- See en.wikipedia.org/wiki/%C5%8Ckuma_Shigenobu
- Okungbowa, Suyi Davies (fl. 2010s) (stories)
- See suyidavies.com
- Olander, Joseph D(avid) (1939- ) (stories) (assoc.)
- See www.sf-encyclopedia.com/entry/olander_joseph_d
- OLaughlin, John Callan (1873-1949) (stories)
- See en.wikipedia.org/wiki/John_Callan_O%27Laughlin
- Old Scout, An; house pseudonym (fl. 1910s-1920s) (stories)
- See www.sf-encyclopedia.com/entry/old_scout_an
- Olde Heuvelt, Thomas (1983- ) (stories)
- See en.wikipedia.org/wiki/Thomas_Olde_Heuvelt
- Olde, Nicholas; pseudonym of Amian Lister Champneys (1879-1951) (stories)
- See desturmobed.blogspot.com/2019/03/nicholas-olde.html
- Older, Daniel José (1980- ) (stories) (assoc.)
- See ghoststar.net
- Older, Mrs. Fremont [i.e., Cora Miranda Baggerly Older] (1875-1968) (stories)
- See www.findagrave.com/cgi-bin/fg.cgi?page=gr&GRid=95828581
- Older, Malka (fl. 2010s) (stories)
- See us.macmillan.com/author/malkaolder
- Olderman, Murray (1922- ) (stories)
- See en.wikipedia.org/wiki/Murray_Olderman
- Oldfield, Barney [i.e., Berna Eli Oldfield] (1878-1946) (stories)
- See en.wikipedia.org/wiki/Barney_Oldfield
- Oldfield, Claude Houghton (1889-1961) (stories)
- Born in Sevenoaks, Kent, England; chartered accountant, civil servant and writer.
- Oldknow, Antony (fl. 1990s-2010s) (stories)
- See www.enmu.edu/about/mmemo/2012/april%202
- Oldman, Gary (Leonard) (1958- ) (stories) (assoc.)
- See en.wikipedia.org/wiki/Gary_Oldman
- Oldmeadow, Ernest (James Francis) (1867-1949) (stories)
- See www.sf-encyclopedia.com/entry/oldmeadow_ernest
- Olds, Sharon (1942- ) (stories)
- See en.wikipedia.org/wiki/Sharon_Olds
- Oldys, William (1696-1761) (stories)
- See en.wikipedia.org/wiki/William_Oldys
- OLeary, Brian (Todd) (1940- ) (stories)
- See www.sf-encyclopedia.com/entry/oleary_brian
- OLeary, Frank (1902- ) (stories)
- Ex-convict; served time in Sing Sing for robbery; co-authored a book on prison dialect. Not to be confused with confused with animator and writer Frank OLeary (1922- ). Born in New York City.
- OLeary, Mike (fl. 1930s-1940s) (stories)
- Not to be confused with British Army officer Michael OLeary (1888-1961).
- OLeary, P(atrick) R. (fl. 2010s) (stories)
- See proleary.com
- OLeary, Patrick (1952- ) (stories) (assoc.)
- See www.sf-encyclopedia.com/entry/oleary_patrick
- OLeary, Timothy (fl. 2010s) (stories)
- See timothyolearylit.com
- Oleastri, Luca (fl. 2010s) (art)
- See www.innovari.it
- Olejniczak, Patryk (fl. 2010s) (art)
- See patryk-garrett.deviantart.com
- Olerich, Henry (1851-1927) (stories)
- See www.sf-encyclopedia.com/entry/olerich_henry
- Olesker, J(ack) Bradford (1949- ) (stories)
- See www.sf-encyclopedia.com/entry/olesker_j_bradford
- Olga of Greece, Queen (1851-1926) (stories) (assoc.)
- See en.wikipedia.org/wiki/Olga_Constantinovna_of_Russia
- Oliphant, Ronald (1884-1968) (stories) (assoc.)
- See freespace.virgin.net/audrey.parnhamandco/Bhe/Laurie1.htm
- Oliva, Alexandra (fl. 2010s) (stories) (assoc.)
- See www.alexandraoliva.com
- Oliver, Anton M(aracek) (1888-1977?) (stories)
- See tellersofweirdtales.blogspot.co.uk/2013/12/anton-m-oliver-1888-1977.html
- Oliver, Carolyn (fl. 2010s) (stories)
- See carolynoliver.net
- Oliver, (Symmes) Chad(wick) (1928-1993) (stories) (assoc.)
- See www.sf-encyclopedia.com/entry/oliver_chad
- Oliver, Eleanor (fl. 1920s) (stories)
- From Elberton, Georgia.
- Oliver, Harry (fl. 1940s) (stories)
- Not the Oscar-winning movie director (1888?-1973) who became a desert hermit.
- Oliver, J(ohn) H(artman) (1871-1942?) (stories)
- Tutor.
- Oliver, Jonathan (fl. 2000s-2010s) (stories)
- See jonoliverwriter.blogspot.co.uk
- Oliver, Kelly (1958- ) (stories) (assoc.)
- See en.wikipedia.org/wiki/Kelly_Oliver
- Oliver, Lauren (fl. 2010s) (stories) (assoc.)
- See www.sf-encyclopedia.com/entry/oliver_lauren
- Oliver, Lunsford Errett (1889-1978) (stories)
- See en.wikipedia.org/wiki/Lunsford_E._Oliver
- Oliver, Mary (1935-2019) (stories)
- See en.wikipedia.org/wiki/Mary_Oliver
- Oliver, S(amuel) Pasfield (1838-1907) (stories)
- See en.wikipedia.org/wiki/Samuel_Pasfield_Oliver
- Olivers, Thomas (1725-1799) (stories) (assoc.)
- See en.wikipedia.org/wiki/Thomas_Olivers
- Olivier, Laurence (Kerr, Baron Olivier) (1907-1989) (stories) (assoc.)
- See en.wikipedia.org/wiki/Laurence_Olivier
- Olivieri, Irene Hardwicke (fl. 2000s-2010s) (art)
- See www.irenehardwickeolivieri.com
- Ollerman, Rick [i.e., Richard Carter Ollerman] (1963- ) (stories) (assoc.)
- Executive of an advertising agency in Florida.
- Ollier, Edmund (1827-1886) (stories)
- See en.wikipedia.org/wiki/Edmund_Ollier
- Ollivant, Alfred (1874-1927) (stories)
- See www.sf-encyclopedia.com/entry/ollivant_alfred
- Ollivier, Émile (1825-1913) (stories)
- See en.wikipedia.org/wiki/Émile_Ollivier
- Olmsted, Harry F(rancis) (1889-1970) (stories) (assoc.)
- Born August 10, 1889 in Los Angeles; worked as a civil engineer before turning to fiction; claimed to have sold 1200 stories; died April 2, 1970 in Riverside, California.
- Olmsted, (Edgar) Stanley (1877-1939) (stories)
- See books.google.com/books?id=qkJEAAAAMAAJ&pg=PA433&lpg=PA433&dq=%22Stanley+Olmsted%22+writer&source=bl&ots=5Kl0i7lT0B&sig=68-Tlf3AW5xZmJStdy8arT-rGJ4&hl=en&sa=X&ved=0ahUKEwjX3I-gr8DTAhUT32MKHdBdBcAQ6AEIJDAB#v=onepage&q=%22Stanley%20Olmsted%22%20writer&f=false
- Olsa, Jaroslav, Jr. (1964- ) (stories)
- See www.sf-encyclopedia.com/entry/olsa_jaroslav_jr