- O’Brien, Christopher M. (fl. 2000s-2010s) (items) (chron.)
- See fancyclopedia.org/Christopher_M._O'Brien
- O’Brien, Dan(iel) (1947- ) (items) (chron.)
- See en.wikipedia.org/wiki/Dan_O'Brien_(author)
- O’Brien, David Wright (1918-1944); used pseudonyms Alexander Blade & Clee Garson (items) (chron.)
- See www.sf-encyclopedia.com/entry/obrien_david_wright
- O’Brien, (Michael) Fitz-James (1828-1862) (items) (chron.)
- See www.sf-encyclopedia.com/entry/obrien_fitz-james
- O’Brien, James (fl. 2010s) (items) (chron.)
- See www.drumlitmag.com/index.php?page=contributors&display=469
- O’Brien, James Edward (fl. 2010s-2020s) (items) (chron.)
- See jamesedwardobrien.wordpress.com
- O’Brien, Kevin L. (fl. 2000s-2020s) (items) (chron.)
- See www.goodreads.com/author/show/335131.Kevin_L_O_Brien
- O’Brien, Phil; pseudonym of Philomena Muinzer (fl. 1980s-1990s) (items)
- See en.wikipedia.org/wiki/Memories_of_the_Irish-Israeli_War
- O’Brien, Richard J. (fl. 2000s-2010s) (items) (chron.)
- See obrienwriter.com
- O’Brien, Robert C.; pseudonym of Robert Leslie Carroll Conly (1922-1973) (items)
- See www.sf-encyclopedia.com/entry/obrien_robert_c
- O’Brien, Sean (fl. 2010s) (items) (chron.)
- See www.seanobrienauthor.com
- Obruchev, Vladimir A(fanasevich) (1863-1956) (items)
- See www.sf-encyclopedia.com/entry/obruchev_vladimir_a
- Ocampo, Victor Fernando R. (fl. 1990s-2010s) (items) (chron.)
- See vrocampo.com
- Occhipinti, Joe (fl. 2010s) (items) (chron.)
- See www.joeocchipinti.net
- Ochse, Weston (1965-2023) (items) (chron.)
- See en.wikipedia.org/wiki/Weston_Ochse
- Ochsner, Gina (1970- ) (items)
- See en.wikipedia.org/wiki/Gina_Ochsner
- Ocker, David (fl. 1980s-2010s) (items)
- See mixedmeters.com
- O’Connell, Jack (1959-2024) (items) (chron.)
- See www.sf-encyclopedia.com/entry/oconnell_jack
- O’Connell, Jay (fl. 2010s-2020s) (items) (chron.)
- See www.jayoconnell.com
- O’Connell, Tabitha (fl. 2010s) (items) (chron.)
- See tjoconnell.wordpress.com
- O’Connor, Kate (1982-) (items) (chron.)
- See kateoconnor3.wordpress.com
- O’Connor, William (Todd) (1970-2018) (items)
- See en.wikipedia.org/wiki/William_O'Connor_(artist)
- O’Conor, Norreys Jephson (1885-1958) (items) (chron.)
- See snaccooperative.org/ark:/99166/w69w0gxg
- Odasso, Adrienne J. (fl. 2000s-2020s) (items) (chron.)
- See ajodasso.livejournal.com
- Odeh, Beesan (fl. 2010s) (items) (chron.)
- See www.worldswithoutend.com/author.asp?ID=5756
- O’Dell, Leslie Ann (fl. 2010s) (items) (chron.)
- See www.leslieannodell.com
- Odell, Minnie (1864-1940); also known as Aurelia M. Michener; used pseudonym Minna Irving (items) (chron.)
- See tellersofweirdtales.blogspot.com/2017/04/minna-irving-1857-1940.html
- Odell, Sandra M. (fl. 2010s-2020s) (items) (chron.)
- See sandramodell.com
- Oden, Scott (1967- ) (items) (chron.)
- See en.wikipedia.org/wiki/Scott_Oden
- Odier, Daniel (Robert) (1945- ) (items)
- See en.wikipedia.org/wiki/Daniel_Odier
- Odom, Mel(vin Lewis, III) (1957- ) (items) (chron.)
- See www.sf-encyclopedia.com/entry/odom_mel
- O’Donnell, Hugh J. (fl. 2010s-2020s) (items) (chron.)
- See hughjodonnell.com
- O’Donnell, Kevin, Jr. (1950-2012) (items) (chron.)
- See www.sf-encyclopedia.com/entry/odonnell_kevin_jr
- O’Donoghue, Eamon (fl. 2010s) (items) (chron.)
- See www.eamonart.com
- O’Driscoll, Dan J. (fl. 2000s-2020s) (items) (chron.)
- See www.djostudio.com
- Oet, Rainie (fl. 2020s) (items) (chron.)
- See www.rainieoet.com
- Offen, Ron(ald C.) (1930-2010) (items) (chron.)
- See en.wikipedia.org/wiki/Ron_Offen
- Offutt, Andrew J(efferson, V) (1934-2013); used pseudonym John Cleve (items) (chron.)
- See www.sf-encyclopedia.com/entry/offutt_andrew_j
- Ofori-Atta, Nana Afadua (fl. 2020s) (items) (chron.)
- See www.fantasy-magazine.com/fm/admin/authors/nana-afadua-ofori-atta
- Oga, Takeshi (fl. 2010s) (items) (chron.)
- See www.takeshioga.com
- Ogamba, Frances (fl. 2020s) (items) (chron.)
- See en.wikipedia.org/wiki/Frances_Ogamba
- Ogan, George (F.) (1912-1983) (items) (chron.)
- Writer and teacher. Born in Kirkwood, Missouri; lived in Louisiana.
- Ogan, Margaret (E. Nettles) (1923-1979) (items) (chron.)
- Teacher and writer, born in Columbia, Louisiana.
- Ogas, Ogi (Jonathan) (1971- ) (items)
- See en.wikipedia.org/wiki/Ogi_Ogas
- Ogawa, Issui; pseudonym (1975- ) (items) (chron.)
- See www.sf-encyclopedia.com/entry/ogawa_issui
- Ogden, Aimee (fl. 2010s-2020s) (items) (chron.)
- See aimeeogdenwrites.wordpress.com
- Oghenekaro, Omodero David (fl. 2020s) (items) (chron.)
- See strangehorizons.com/author/omodero-david-oghenekaro
- Oglesby, W(illiam) H. Ellis (1966- ) (items) (chron.)
- Freelance writer in Atlanta, Georgia.
- Ognibene, Peter J(ohn) (1941- ) (items) (chron.)
- See www.sf-encyclopedia.com/entry/ognibene_peter_j
- Ó Guilín, Peadar (fl. 1990s-2010s) (items) (chron.)
- See www.sf-encyclopedia.com/entry/o_guilin_peadar
- Ògúnyẹmí, Ernest O. (fl. 2020s) (items) (chron.)
- See www.thedarkmagazine.com/authors/ernest-o-ogunyem
- Ogurek, Douglas J.; pseudonym (fl. 2010s-2020s) (items) (chron.)
- See douglasjogurek.weebly.com
- Ogutsch, Edith (1929-1990) (items) (chron.)
- See tellersofweirdtales.blogspot.co.uk/2016/01/edith-ogutsch-1929-1990.html
- Oh, Susie (fl. 2010s) (items) (chron.)
- See susieoh.net
- Oh, Temi (fl. 2010s) (items)
- See www.theonlytemioh.com
- Ohlson, (Douglas) Hereward (1907-1955) (items)
- See www.sf-encyclopedia.com/entry/ohlson_hereward
- Ohnaka, Kathryn (fl. 2010s) (items) (chron.)
- See www.kathrynohnaka.com
- Okafor, Marycynthia Chinwe (fl. 2020s) (items) (chron.)
- See www.africanwriter.com/author/okamarychinfor
- O’Keefe, Claudia (Diane) (1958- ) (items) (chron.)
- See www.sf-encyclopedia.com/entry/okeefe_claudia
- O’Keefe, Megan E. (fl. 2010s) (items) (chron.)
- See meganokeefe.com
- O’Keefe, Rose (fl. 2010s) (items) (chron.)
- See litreactor.com/team/rose-okeefe
- Okorafor, Nnedi(mma Nkemdili) (1974- ); previously known as Nnedima Okorafor-Mbachu (items) (chron.)
- See en.wikipedia.org/wiki/Nnedi_Okorafor
- O’Kun, Lan (1932-2020) (items)
- See deadline.com/2020/01/lan-okun-obituary-collaborator-with-shari-lewis-dies-at-87-1202827877/
- Okungbowa, Suyi Davies; [working name of Osasuyi Okungbowa] (1989- ) (items) (chron.)
- See sf-encyclopedia.com/entry/okungbowa_suyi_davies
- Olander, Joseph D(avid) (1939- ) (items)
- See www.sf-encyclopedia.com/entry/olander_joseph_d
- Olde Heuvelt, Thomas (1983- ) (items) (chron.)
- See en.wikipedia.org/wiki/Thomas_Olde_Heuvelt
- Older, Daniel José (1980- ) (items) (chron.)
- See ghoststar.net