| O Dia é Nosso | — | comedy film | Brazil |
| O gamos tis koris mou | Nikos Koutelidakis | comedy film | Greece |
| O Picasso | Camille Coudari, Gilles Carle | documentary film | Canada |
| O Que Resta | — | drama film | Brazil |
| O Stratis parastratise | Kostas Karagiannis | comedy film | Greece |
| O thanatos tha xanarthi | Errikos Thalassinos | drama film | Greece |
| O Ébrio | Gilda de Abreu | drama film, musical film | Brazil |
| O'Romeo | Vishal Bhardwaj | action thriller | India |
| O. Henry's Full House | Henry King, Jean Negulesco, Henry Hathaway, Howard Hawks, Henry Koster | drama film, comedy film, Western film, Christmas film, adventure film | United States |
| O. K., Leave It to Me, Boss...! | Petr Schulhoff | comedy film | Czechoslovakia |
| O.C. and Stiggs | Robert Altman | teen film | United States |
| O.K. ... Laliberté | Marcel Carrière | comedy drama | Canada |
| Objection | Andrzej Trzos-Rastawiecki | — | Poland |
| Objective, Burma! | Raoul Walsh | action film, war film | United States |
| Oblivion 2: Backlash | Sam Irvin | Western film, science fiction film | United States |
| Oblivion Island: Haruka and the Magic Mirror | Shinsuke Sato | teen film, drama film | Japan |
| Obratnaya svyaz | Aleksey Nuzhny | comedy film | Russia |
| Obsession | Brian De Palma | psychological thriller film, suspense film, crime drama film, mystery film, drama film, crime thriller film, neo-noir, thriller film, psychological drama film, crime film | United States |
| Ocean's 8 | Gary Ross | comedy film, action film, thriller film, heist film, female buddy film, crime film | United States |
| Ocean's Eleven | Steven Soderbergh | mystery film, comedy film, action film, adventure film, heist film | United States, Australia |
| October Baby | Andrew Erwin, Jon Erwin | drama film | United States |
| Oda | Rafiz Ismailov, Vahid Talıbov | musical film | Soviet Union |
| Odd Jobs | Stélios Tatassópoulos | comedy film | Greece |
| Oddity | Damian McCarthy | horror film, thriller film, supernatural film | Ireland |
| Odessa | Jean Lods | documentary film | Soviet Union |
| Odiyan | V. A. Shrikumar Menon | fantasy film | India |
| Oedipus Rex | Pier Paolo Pasolini | drama film | Italy |
| Oeil pour oeil | André Cayatte | drama film | France, Italy |
| Of Freaks and Men | Aleksei Balabanov | erotic film, comedy drama | Russia |
| Of Human Bondage | Edmund Goulding | drama film | United States |
| Of Mice and Men | Gary Sinise | drama film, historical drama | United States |
| Off the Map | Tiina Lymi | romance film, drama film, comedy film, road movie, crime film | Finland |
| Office Christmas Party | Josh Gordon, Will Speck | comedy film, Christmas film | United States |
| Office Romance | Eldar Ryazanov | drama film, romantic comedy | Soviet Union |
| Office Trap Love | — | romance film, drama film | United States |
| Office Uprising | Lin Oeding | horror film, action comedy film | United States |
| Officer 666 | Fred Niblo | — | — |
| Official Bounty Hunter Parody 2 | Reno D'Angelo | pornographic parody film, pornographic film | United States |
| Offline Mode | Fausto Brizzi | comedy film | Italy |
| Oggi sposi | Luca Lucini | romantic comedy | Italy |
| Ogniomistrz Kaleń | Czesław Petelski, Ewa Petelska | drama film | Poland |
| Ogonki | Boris Rytsarev | drama film, children's film | Soviet Union |
| Oh Boy! | Orlow Seunke | comedy film | Netherlands |
| Oh Dad, Poor Dad, Mama's Hung You in the Closet and I'm Feelin' So Sad | Richard Quine | comedy film | United States |
| Oh! Heavenly Dog | Joe Camp | fantasy film, comedy film | United States |
| Oh! Susanna | Joseph Kane | Western film | United States |
| Oh, God! Book II | Gilbert Cates | fantasy film, comedy film, speculative fiction film | United States |
| Oh, Mabel Behave | Ford Sterling | — | — |
| Oh, Ramona! | Cristina Jacob | romantic comedy film | Romania |
| Oh, You Beautiful Doll | John M. Stahl | biographical film, musical film | United States |
| Oiseau de printemps, hirondelle d'hiver | Georges Denola | — | — |
| Okashiratsuki | Mikiya Sanada | — | Japan |
| Okean Elzy: Stormwatch | Artem Hryhorian | biographical film, documentary film | Ukraine |
| Okinawa Rendez-vous | Gordon Chan | romantic comedy | Hong Kong |
| Okuni and Gohei | Mikio Naruse | drama film | Japan |
| Old Baron of Rautakylä | Karl Fager | — | — |
| Old Bill Through the Ages | Thomas Bentley | — | — |
| Old Dads | Bill Burr | comedy film | United States |
| Old Guy | Simon West | action comedy film | United States |
| Old Hags | Eldar Ryazanov | crime comedy film | Russia |
| Old Home Week | Victor Heerman | — | — |
| Old Khottabych | Gennady Kazansky | — | — |
| Old Man Bebo | Carlos Carcas | documentary film | Spain |
| Old Mother Riley Joins Up | Maclean Rogers | — | — |
| Old Mother Riley Overseas | Oswald Mitchell | comedy film | United Kingdom |
| Old Mother Riley's Circus | Thomas Bentley | — | — |
| Old Overland Trail | William Witney | Western film | United States |
| Old San Francisco | Alan Crosland | — | — |
| Old School | Todd Phillips | comedy film | United States |
| Old Shatterhand | Hugo Fregonese | Western film, adventure film | France, Germany, Italy |
| Old Spanish Customers | Lupino Lane | — | — |
| Old Walls | Viktor Tregubovich | romance film, drama film | Soviet Union |
| Old Well | Wu Tianming | romantic drama film | People's Republic of China |
| Old-fashioned Tango | Alexander Belinsky, Dmitry Bryantsev | comedy film, ballet film, musical film | Soviet Union |
| Old-fashioned Tricks | Aleksandr Pankratov | comedy film | Soviet Union |
| Older Office Lady: Using Her Seductive Tongue | Yumi Yoshiyuki | pink film, pornographic film | Japan |
| Oleg | Juris Kursietis | drama film | Latvia, Belgium, Lithuania |
| Oleko Dundich | Leonid Lukov | — | — |
| Olga i Konstantin | Yevgeny Mezentsev | comedy film | Soviet Union |
| Oli Vilakku | Tapi Chanakya | crime film | India |
| Oliver & Company | George Scribner | family film, children's film, adventure film, buddy film, musical film, comedy drama | United States |
| Oliver's Universe | Alexis Morante | coming-of-age film | Spain |
| Ollie Alexander Tiddly-Om-Pom-Pom | Anne-Marie Nørholm | children's film | Norway |
| Olli’s Apprenticeship | Teuvo Puro | — | — |
| Olsen-banden og Dynamitt-Harry | Ove Kant | crime comedy film | Norway |
| Olsenbanden for full musikk | Knut Bohwim | crime comedy film | Norway |
| Olsenbanden og Dynamitt-Harry går amok | Knut Bohwim | crime comedy film | Norway |
| Om Shanti Om | Farah Khan | romance film, fantasy film | India |
| Omar Khayyam | William Dieterle | biographical film | United States |
| Ombyte av tåg | Hasse Ekman | drama film | Sweden |
| Omen III: The Final Conflict | Graham Baker | political thriller film, horror film | United Kingdom, United States |
| Omena putoaa... | Valentin Vaala | — | — |
| Omerta 6/12 | Aku Louhimies | action film | Finland |
| OMG | — | romantic comedy | Philippines |
| On a Clear Day You Can See Forever | Vincente Minnelli | romantic comedy film, drama film, fantasy film, musical film, comedy drama | United States |
| On a marché sur Bangkok | Olivier Baroux | comedy film | France |
| On a Narrow Bridge | Nissim Dayan | drama film | Israel |
| On Again-Off Again | Edward F. Cline | — | — |
| On Approval | Clive Brook | — | — |
| On Her Majesty's Secret Service | Peter R. Hunt | action film, spy film, thriller film, Christmas film, adventure film, crime film | United Kingdom |
| On My Way | Emmanuelle Bercot | drama film, comedy film, road movie | France |
| On Our Selection | Ken G. Hall | — | — |
| On Set With Riley Reid | — | virtual reality pornographic film | United States |
| On the Beach | Stanley Kramer | drama film, post-apocalyptic film, dystopian film, science fiction film, disaster film | United States, Australia |
| On the Heights | Luise Fleck | — | — |
| On the Loose | Hal Roach | comedy film, buddy film | United States |
| On the Pulse | Alix Delaporte | drama film | France, Belgium |
| On the Quiet | Chester Withey | — | — |
| On the Riviera | Walter Lang | musical film, romantic comedy | United States |
| On the Road to Timbuktu: Explorers in Africa | Jean-Claude Lubtchansky | documentary film | France |
| On the Rocks | Sofia Coppola | comedy drama | United States |
| On the Same Planet | Ilya Olshvanger | drama film, biographical film | Soviet Union |
| On the Sunny Side | Ralf Kirsten | musical film | East Germany |
| On the Threshold of Space | Robert D. Webb | — | — |
| On the Trail of Blood | Petr Schulhoff | crime film | Czechoslovakia |
| On the Waterfront | Elia Kazan | drama film, thriller film, crime film | United States |
| On Thin Ice | Damir Vyatich-Berezhnykh | spy film, adventure film, war film | Soviet Union |
| On Trial | Archie Mayo | — | — |
| On Upper Maslovka Street | Konstantin Khudyakov | drama film | Russia |
| On Ze Boulevard | Harry F. Millarde | — | — |
| Once a Doctor | William Clemens | drama film | United States |
| Once a Plumber | Eddie Lyons | — | — |
| Once a Princess | Laurice Guillen | romance film | Philippines |
| Once Around | Lasse Hallström | drama film, romantic comedy | United States |
| Once Bitten | Howard Storm | comedy film, vampire film, comedy horror | United States |
| Once in a Lifetime | Russell Mack | comedy film | United States |
| Once There Was a Girl | Viktor Eisymont | — | — |
| Once Upon a Dog | Eduard Nazarov | comedy film, children's film, adventure film | Soviet Union |
| Once Upon a Horse... | Hal Kanter | Western film | United States |
| Once Upon a Time | Thomas Bentley | — | — |
| Once Upon a Time in China and America | Sammo Hung | martial arts film, action film, biographical film | Hong Kong |
| Once Upon a Time in China IV | Yuen Bun | martial arts film, biographical film | Hong Kong |
| Once Upon a Time in Mesopotamia | Jean-Claude Lubtchansky | documentary film | France |
| Once Upon a Time in Mexico | Robert Rodriguez | action film, thriller film, contemporary Western film, crime film | United States |
| Once Upon a Time in Mumbaai | Milan Luthria | action film | India |
| Once Upon a Time in the West | Sergio Leone | drama film, Western film, action film, melodrama, Spaghetti Western, flashback film, epic film | United States, Italy |
| Once Upon a Time Twenty Years Later | Yuri Yegorov | comedy drama | Soviet Union |
| Once You Give Away Your Heart | Johannes Guter | — | — |
| Once You're Born You Can No Longer Hide | Marco Tullio Giordana | drama film | France, United Kingdom, Italy |
| One | Birsa Dasgupta | action film, crime thriller film | India |
| One Cab's Family | Tex Avery | family film, comedy film | United States |
| One Crazy Summer | Savage Steve Holland | romantic comedy film | United States |
| One Crowded Night | Irving Reis | drama film | United States |
| One Direction: This Is Us | Morgan Spurlock | documentary film | United Kingdom, United States |
| One Eight Seven | Kevin Reynolds | drama film, thriller film, hood film, crime film | United States |
| One Exciting Night | Walter Forde | — | — |
| One Exciting Week | William Beaudine | comedy film | United States |
| One Fine Day | — | drama film | Indonesia |
| One Fine Spring Day | Hur Jin-ho | romance film | South Korea |
| One for All | David Ilundain Areso | drama film | Spain |
| One for the Road | Nattawut Poonpiriya | drama film | People's Republic of China, Hong Kong, Thailand |
| One Good Cop | Heywood Gould | drama film, action film, crime film | United States |
| One Good Turn | Arthur Maude | comedy film | United Kingdom |
| One Hundred Days After Childhood | Sergei Solovyov | romance film, teen film, drama film | Soviet Union |
| One in a Million | Sidney Lanfield | musical film, romantic comedy | United States |
| One in the Chamber | William Kaufman | action film | United States |
| One Increasing Purpose | Harry Beaumont | — | — |
| One Is a Lonely Number | Mel Stuart | drama film | United States |
| One Life and Two Trails | Alberto Arvelo | drama film | Venezuela |
| One Little Indian | Bernard McEveety | comedy film, Western film | United States |
| One Magic Christmas | Phillip Borsos | drama film, fantasy film, children's film, Christmas film | Canada, United States |
| One Million Years B.C. | Don Chaffey | fantasy film, adventure film | United Kingdom |
| One Missed Call | Éric Valette | horror film, ghost film | Japan, Germany, United States |
| One More American | William Churchill deMille | — | — |
| One Night in the Tropics | A. Edward Sutherland | comedy film, musical film | United States |
| One Night Stand | Allan King | drama film, thriller film | Canada |
| One Night Stand | Mike Figgis | romance film, drama film | United States |
| One of Our Dinosaurs Is Missing | Robert Stevenson | comedy film, neo-noir | United Kingdom, United States |
| One of Them Days | Lawrence Lamont | comedy film, female buddy film, buddy film | United States |
| One Piece Movie: The Desert Princess and the Pirates: Adventures in Alabasta | Takahiro Imamura | drama film, comedy film, action film, adventure film | Japan |
| One Piece: Baron Omatsuri and the Secret Island | Mamoru Hosoda | comedy film, action film, horror film, thriller film, adventure film | Japan |
| One Piece: Stampede | Takashi Ōtsuka | fantasy film, action film, anime film, adventure film | Japan |
| One Piece: The Cursed Holy Sword | Kazuhisa Takenouchi | comedy film, action film, adventure film | Japan |
| One Second for a Feat | Gil-sen Om, Eldor Urazbayev | historical film | Soviet Union, North Korea |
| One Stolen Night | Robert Ensminger | — | — |
| One Street Organ, One Life | Sokrates Kapsaskis | drama film | Greece |
| One Swallow Does Not Make a Summer | Hasse Ekman | comedy film | Sweden |
| One Way Ticket | Herbert Biberman | drama film | United States |
| One Win | Shin Yeon-shick | sport film | South Korea |
| Only "Old Men" Are Going Into Battle | Leonid Bykov | war film, musical film, comedy drama | Soviet Union |
| Only a Miracle | Olena Karetnyk | fantasy film, adventure film | Ukraine |
| Only Angels Have Wings | Howard Hawks | drama film | United States |
| Only the Brave | Frank Tuttle | historical film | United States |
| Onni etsii asuntoa | Thure Bahne | comedy film | Finland |
| Onoda | Arthur Harari | biographical drama film, drama film, adventure film, war film | France, Japan, Germany, Belgium, Italy, Cambodia |
| Ooh… You Are Awful | Cliff Owen | independent film | United Kingdom |
| Ooyala | S. V. Krishna Reddy | — | India |
| Op Hoop van Zegen | Alex Benno, Louis Saalborn | drama film | Netherlands |
| Open Future | Petter Vennerød, Svend Wam | drama film | Norway |
| Open Season | Anthony Stacchi, Jill Culton, Roger Allers | family film, comedy film, flashback film, buddy film, musical film | United States |
| Open Windows | Nacho Vigalondo | thriller film | Spain, United States |
| Operasjon V for vanvidd | Rolf Clemens | crime film | Norway |
| Operation Cupid | Charles Saunders | comedy film | United Kingdom |
| Operation Daybreak | Lewis Gilbert | drama film, adventure film, war film | United States, Czechoslovakia, Yugoslavia |
| Operation Mekong | Dante Lam | action film, adventure film, crime film | People's Republic of China, Hong Kong |
| Opettajatar seikkailee | Aarne Tarkas | comedy film | Finland |
| Opium and the Kung-Fu Master | Tong Gai | martial arts film, thriller film | Hong Kong |
| Opticheskie perekladki | Vladimir Nikitchenko | — | — |
| Orange Blossom | Henry Roussel | comedy drama | France |
| Orange County | Jake Kasdan | coming-of-age film, teen film, comedy film | United States |
| Orangerie | Benoît Majerus, Anne Schiltz | documentary film | Luxembourg |
| Orca | Michael Anderson | natural horror film, horror film, thriller film, adventure film, independent film, disaster film | Italy, Netherlands |
| Orchids and Ermine | Alfred Santell | — | — |
| Ordinary People | Robert Redford | drama film | United States |
| Organ Child | Chieh Shueh-bin | thriller film, crime film | Taiwan |
| Orgy World 7 | T. T. Boy | pornographic film | United States |
| Orient Express | Paul Martin | drama film | United States |
| Origami | Patrick Demers | fiction film, drama film | Canada |
| Original Sin | Michael Cristofer | romance film, mystery film, drama film, erotic thriller, erotic film, crime film | United States, Mexico |
| Orphan of the Wilderness | Ken G. Hall | — | — |
| Orpopojan valssi | Ville Salminen | biographical film | Finland |
| Oru Kidayin Karunai Manu | Suresh Sangaiah | comedy drama | India |
| Oru Sundariyude Katha | Thoppil Bhasi | — | India |
| Oryu's Passion: Bondage Skin | — | pink film | Japan |
| Os fenómenos | Alfonso Zarauza | drama film | Spain |
| Oscar | John Landis | screwball comedy film, crime film | United States |
| Oscar | Édouard Molinaro | comedy film | France |
| Osenniie svadby | Boris Yashin | drama film | Soviet Union |
| Osetinskaya legenda | Azanbek Dzhanaev | historical film, melodrama | Soviet Union |
| Oshi, Mankai | Hidekazu Takahara | pink film | Japan |
| Osman Pazarlama | Togan Gökbakar | comedy film | Turkey |
| Osmondagi bolalar | Zulfikar Musakov | Western film | Uzbekistan |
| Osmondagi bolalar 2 | Zulfikar Musakov | — | Uzbekistan |
| Oss atomforskere i mellom | Titus Vibe-Müller | crime comedy film | Norway |
| Ostap Bandura | Vladimir Gardin | — | — |
| Ostrov vozrozhdeniya | Rustem Abdrashev | drama film | Kazakhstan |
| Otello | — | — | Soviet Union |
| Otello | Camillo De Riso | — | — |
| Othello | Sergei Yutkevich | romance film, drama film | Soviet Union |
| Other Men's Daughters | Carl Harbaugh | — | — |
| Other Men's Women | William A. Wellman | — | — |
| Other People's Relatives | Mikhail Schweitzer | — | — |
| Otherhood | Cindy Chupack | comedy film | United Kingdom, United States |
| Our Agent Tiger | Claude Chabrol | mystery film, comedy film, spy film, adventure film, crime film | France, Spain, Italy |
| Our Body | Han Ka-ram | drama film | South Korea |
| Our Erika | German Golub | sport film, biographical film | Estonia |
| Our Father, Our President | Manuel Huerga | biographical drama film, flashback film, political drama | Spain |
| Our Idiot Brother | Jesse Peretz | drama film, comedy film, LGBTQ-related film | United States |
| Our Little Girl | John S. Robertson | — | — |
| Our Little Wife | Paul Verhoeven | comedy film | Germany, Italy |
| Our Man Flint | Daniel Mann | science fiction film, parody film, science fiction comedy | United States |
| Our Man in Havana | Carol Reed | drama film, spy film | United Kingdom, United States |
| Our Miss Fred | Bob Kellett | LGBTQ-related film | United Kingdom |
| Our Mother's House | Jack Clayton | drama film | United Kingdom |
| Our Sisters-in-Law | René Richard Cyr | comedy film, musical film | Canada |
| Our Vines Have Tender Grapes | Roy Rowland | — | — |
| Out All Night | Sam Taylor | comedy film | United States |
| Out for Justice | John Flynn | martial arts film, action film, crime thriller film | United States |
| Out of Breath | Sirus Alvand | — | Iran |
| Out of Paradise | Batbayar Chogsom | drama film | Switzerland, Mongolia |
| Out of the Blue | Gene Gerrard | — | — |
| Out of the Furnace | Scott Cooper | drama film, thriller film, prison film | United States |
| Out of the Shadow | Émile Chautard | — | — |
| Out on a Limb | Francis Veber | comedy film | United States |
| Out to Win | Denison Clift | — | — |
| Outcast | Chester Withey | — | — |
| Outcast of the Islands | Carol Reed | drama film | United Kingdom |
| Outland | Peter Hyams | action film, adventure film, science fiction film | United Kingdom |
| Outlander | Howard McCain | sword-and-sandal film, fantasy film, action film, medieval film, science fiction film | United States |
| Outlaws | Daniel Monzón | thriller film | Spain |
| Outlaws of Cherokee Trail | Lester Orlebeck | — | — |
| Outrage | Takeshi Kitano | drama film, action film, crime film | Japan |
| Outrageous Fortune | Arthur Hiller | comedy film, female buddy film | United States |
| Outside Providence | Michael Corrente | romance film, drama film, romantic comedy | United States |
| Ovejas negras | José María Carreño Bermúdez | black comedy | Spain |
| Over the Garden Wall | John E. Blakeley | comedy film | United Kingdom |
| Over the Moon | Glen Keane | adventure film, musical film | People's Republic of China, United States |
| Overland with Kit Carson | Norman Deming | — | — |
| Ovunque sei | Michele Placido | drama film | Italy |
| Owe akala | S.O.B Agunbiade | — | Nigeria |
| Owl | Kaneto Shindō | mystery film | Japan |
| Oyayubi Sagashi | Naoto Kumazawa | — | Japan |
| Oļegs un Aina | Aleksandrs Leimanis | — | Soviet Union |
| Özlem…Düne, Bugüne, Yarına | Tülay Eratalay | — | Turkey |