| O chyom molchat devushki | Karen Oganesyan | comedy film | Russia |
| O Homem do Futuro | Cláudio Torres | romantic comedy | Brazil |
| O panikos | Stavros Tsiolis | — | Greece |
| O Picasso | Camille Coudari, Gilles Carle | documentary film | Canada |
| O skliros andras | Giannis Dalianidis | comedy film | Greece |
| O strannostyakh lyubvi | Yakov Protazanov | — | — |
| O Stratis parastratise | Kostas Karagiannis | comedy film | Greece |
| O Tempo dos Leopardos | Zdravko Velimirović | drama film | Mozambique, Yugoslavia |
| O Ébrio | Gilda de Abreu | drama film, musical film | Brazil |
| O.C. and Stiggs | Robert Altman | teen film | United States |
| O.K. ... Laliberté | Marcel Carrière | comedy drama | Canada |
| O.K. Connery | Alberto De Martino | parody film | Italy |
| O.K. Garage | Brandon Cole | drama film, comedy drama | United States |
| O.S.S. | Irving Pichel | — | — |
| Oasis | Lee Chang-dong | romance film, drama film | South Korea |
 Oatsurae Jirokichi Koshi | Daisuke Itō | — | — |
 Objective, Burma! | Raoul Walsh | action film, war film | United States |
| Obmanutye | Ada Neretniece | — | Soviet Union |
| Občan Brych | Otakar Vávra | — | — |
| Ocalenie | Edward Żebrowski | drama film | Poland |
| Ocean (film) | Yuri Vyshinsky | drama film | Soviet Union |
| Ocean Waves | Tomomi Mochizuki | romance film | Japan |
| OceanWorld 3D | Jean-Jacques Mantello | nature documentary | United Kingdom |
| October Baby | Andrew Erwin, Jon Erwin | drama film | United States |
 Oculus | Mike Flanagan | horror film, ghost film, psychological horror fiction, supernatural fiction | United States |
| Oczy uroczne | Piotr Szulkin | horror film | Poland |
| Oda | Rafiz Ismailov, Vahid Talıbov | musical film | Soviet Union |
| Oddity | Damian McCarthy | horror film, thriller film, supernatural film | Ireland |
| Odds Against Tomorrow | Robert Wise | drama film, film noir, heist film, crime film | United States |
| Ode to My Father | Yoon Je-kyoon | drama film | South Korea |
 Odette | Giuseppe de Liguoro | — | — |
| Odiyan | V. A. Shrikumar Menon | fantasy film | India |
| Odoru ryū kyūjō | Yasushi Sasaki | — | — |
 Oedipus Rex | Pier Paolo Pasolini | drama film | Italy |
| Oeil pour oeil | André Cayatte | drama film | France, Italy |
| Of Human Bondage | Edmund Goulding | drama film | United States |
| Of Ink and Blood | Alexis Fortier Gauthier, Francis Fortin, Maxim Rheault | fiction film, drama film | Canada |
| Of Mice and Men | Gary Sinise | drama film, historical drama | United States |
| Of Things Supernatural | Jaroslav Mach, Miloš Makovec, Jiří Krejčík | comedy film, anthology film | Czechoslovakia |
| Off Beat | Michael Dinner | romantic comedy | United States |
| Off Limits | George Marshall | comedy film, boxing film | United States |
| Offering | Hanny Saputra | mystery film, horror film | Indonesia |
| Offering to the Storm | Fernando González Molina | thriller film | Spain |
| Office of Magical Forces | Dmitriy Avdeev, Dmytro Avdieiev | family film, fantasy film, comedy film, adventure film | Ukraine |
| Office Trap Love | — | romance film, drama film | United States |
| Officetel - Skillful Ones | Chun Sung-joon | erotic film | South Korea |
| Official Bounty Hunter Parody 4 | Reno D'Angelo | pornographic parody film, pornographic film | United States |
| Official the Silence of the Lambs Parody | Gary Dean Orona | mystery film, comedy film, pornographic parody film, horror film, thriller film, crime film | United States |
| Offside | Serdar Akar | association football film, comedy drama | Turkey |
| Ogaryova Street, Number 6 | Boris Grigoryev | crime film | Soviet Union |
| Ogniomistrz Kaleń | Czesław Petelski, Ewa Petelska | drama film | Poland |
| Ogu and Mampato in Rapa Nui | Alejandro Rojas | fantasy film | Chile |
| Oh Dad, Poor Dad, Mama's Hung You in the Closet and I'm Feelin' So Sad | Richard Quine | comedy film | United States |
| Oh La La! | Anne Fontaine | comedy drama | France |
| Oh Mercy! | Arnaud Desplechin | crime film | France |
| Oh My School! | — | animated film | People's Republic of China |
| Oh Sailor Behave | Archie Mayo | — | — |
| Oh, God! Book II | Gilbert Cates | fantasy film, comedy film, speculative fiction film | United States |
 Oh, Kay! | Mervyn LeRoy | — | — |
| Oh, quina joia! | Ventura Pons | comedy film | Spain |
| Oh, That Nastya! | Yuri Pobedonostsev | family film, children's film | Soviet Union |
| Oiseau de printemps, hirondelle d'hiver | Georges Denola | — | — |
| Ojuse | Tunde Babs | — | Nigeria |
 Ojōsan shachō | Kō Nakahira | — | — |
| Ok Jaanu | Shaad Ali | romance film, drama film | India |
| Okean Elzy: Stormwatch | Artem Hryhorian | biographical film, documentary film | Ukraine |
| OKI - In the Middle of the Ocean | Māris Martinsons | mystery film, drama film | Latvia, United States |
| Okinawa Rendez-vous | Gordon Chan | romantic comedy | Hong Kong |
| Okkadu | Gunasekhar | action film | India |
| Oklahoma Renegades | Nate Watt | — | — |
 Oklahoma! | Fred Zinnemann | musical film | United States |
| Okuni and Gohei | Mikio Naruse | drama film | Japan |
| Ola & Julia | Jan Halldoff | drama film | Sweden |
| Old Bill Through the Ages | Thomas Bentley | — | — |
| Old Fashioned Comedy | Era Savelyeva, Tatyana Berezantseva | romance film, drama film | Soviet Union |
| Old Hags | Eldar Ryazanov | crime comedy film | Russia |
| Old Man Rhythm | Edward Ludwig | musical film | United States |
| Old Mother Riley Detective | Lance Comfort | — | — |
| Old Mother Riley Overseas | Oswald Mitchell | comedy film | United Kingdom |
| Old Overland Trail | William Witney | Western film | United States |
| Old Thieves: The Legend of Artegio | Everardo González | documentary film | Mexico |
| Old-fashioned Tricks | Aleksandr Pankratov | comedy film | Soviet Union |
| Older Office Lady: Using Her Seductive Tongue | Yumi Yoshiyuki | pink film, pornographic film | Japan |
| Oleko Dundich | Leonid Lukov | — | — |
| Oliver's Universe | Alexis Morante | coming-of-age film | Spain |
| Ollie Alexander Tiddly-Om-Pom-Pom | Anne-Marie Nørholm | children's film | Norway |
| Olsen Gang jr. Master Thief tax | Arne Lindtner Næss | comedy film | Norway |
| Olsen-banden og Dynamitt-Harry | Ove Kant | crime comedy film | Norway |
| Olsenbanden | Knut Bohwim | crime comedy film, action comedy film | Norway |
| Olsenbanden for full musikk | Knut Bohwim | crime comedy film | Norway |
| Olsenbandens siste bedrifter | Knut Andersen | crime comedy film | Norway |
| Olympus Has Fallen | Antoine Fuqua | political thriller film, action film, thriller film | United States |
| Olympus: Refuge of Gods | Joe D'Amato | pornographic film | Italy |
| Ombyte av tåg | Hasse Ekman | drama film | Sweden |
| Omena putoaa... | Valentin Vaala | — | — |
| OMG – Oh My God! | Umesh Shukla | fantasy film, trial film, comedy drama | India |
| Omicron | Ugo Gregoretti | comedy film, science fiction film | Italy |
| On Chesil Beach | Dominic Cooke | drama film, melodrama | United Kingdom |
| On Deadly Ground | Steven Seagal | action film | United States |
| On Our Selection | Ken G. Hall | — | — |
| On the Beat | Charles-Olivier Michaud | romantic comedy | Canada |
| On the Buses | Harry Booth | comedy film | United Kingdom, Australia |
| On the Comet | Jan Procházka, Karel Zeman | fantasy film, adventure film, science fiction film | Czechoslovakia |
| On the Fringe | Juan Diego Botto | drama film, thriller film | Spain, Belgium |
| On the Loose | Charles Lederer | — | — |
| On the Mountain of Tai Hang | Shen Dong, Chen Jian, Wei Lian | historical film, war film | People's Republic of China |
| On the Road | Walter Salles, Sam Riley | drama film, LGBTQ-related film, adventure film, road movie | France, United Kingdom, Brazil, Canada, United States, Mexico |
| On the Road to Berlin | Sergei Popov | drama film, war film | Russia |
| On the Road to Timbuktu: Explorers in Africa | Jean-Claude Lubtchansky | documentary film | France |
| On the Steppe | Boriss Bunejev | — | — |
| On the Threshold | Leif Erlsboe | drama film | Norway |
| On the Threshold of Space | Robert D. Webb | — | — |
 On the Town | Stanley Donen, Gene Kelly | musical film | United States |
| On the Trail of Blood | Petr Schulhoff | crime film | Czechoslovakia |
| On the Wrong Trek | Charley Chase | comedy film, buddy film | United States |
| On Thursday and Never Again | Anatoly Efros | romance film, drama film | Soviet Union |
 On Trial | Archie Mayo | — | — |
| On Your Mark | Hayao Miyazaki | science fiction anime and manga | Japan |
| Once | John Carney | musical film | Ireland |
| Once a Princess | Laurice Guillen | romance film | Philippines |
| Once Bitten | Howard Storm | comedy film, vampire film, comedy horror | United States |
 Once in a Lifetime | Marie-Castille Mention Schaar | drama film, comedy drama | France |
| Once in a lifetime | Carlos F. Borcosque | — | — |
| Once in a Lifetime | Russell Mack | comedy film | United States |
| Once in the Summer | Igor Ilyinsky, Khanan Shmain | comedy film | Soviet Union |
 Once There Was a Girl | Viktor Eisymont | — | — |
 Once to Every Woman | Allen Holubar | — | — |
| Once Upon a Forest | Charles Grosvenor | family film, fantasy film | United Kingdom, United States |
| Once Upon a Horse... | Hal Kanter | Western film | United States |
| Once Upon a Studio | Dan Abraham, Trent Correy | crossover fiction, live-action/animated film, fantasy comedy film | United States |
| Once Upon a Time | Zhao Xiaoding | drama film | People's Republic of China |
| Once upon a time | Chaim Halachmi | comedy film, silent film | Mandatory Palestine |
| Once Upon a Time | Alexander Hall | — | — |
| Once Upon a Time in a Battlefield | Lee Joon-ik | drama film, medieval film, war film | South Korea |
| Once Upon a Time in China IV | Yuen Bun | martial arts film, biographical film | Hong Kong |
| Once Upon a Time in Hollywood | Quentin Tarantino | drama film, comedy film, alternate history film, alternate history, black comedy film, comedy drama, crime film | United Kingdom, United States |
| Once Upon a Time in Shanghai | Peng Xiaolian | drama film | People's Republic of China |
 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 an Angel | Vincent Perez | romance film, drama film | France |
| Once You're Born You Can No Longer Hide | Marco Tullio Giordana | drama film | France, United Kingdom, Italy |
| One Chance in One Thousand | Levon Kocharyan | adventure film, war film | Soviet Union |
 One Direction: This Is Us | Morgan Spurlock | documentary film | United Kingdom, United States |
| One Exciting Adventure | Ernst L. Frank | comedy film | United States |
| One for the Road | Paul Trijbits | comedy drama | United Kingdom |
| One from the Heart | Francis Ford Coppola | romance film, drama film, musical film | United States |
| One Good Cop | Heywood Gould | drama film, action film, crime film | United States |
| One Good Turn | John Paddy Carstairs | — | — |
| One Heavenly Night | George Fitzmaurice | — | — |
| One Hundred Men and a Girl | Henry Koster | comedy film, musical film | United States |
| One Is a Lonely Number | Mel Stuart | drama film | United States |
| One Last Dance | Lisa Niemi | romance film, drama film, dance film | Canada, United States |
| One Life and Two Trails | Alberto Arvelo | drama film | Venezuela |
| One Magic Christmas | Phillip Borsos | drama film, fantasy film, children's film, Christmas film | Canada, United States |
| One Man's Journey | John S. Robertson | — | — |
| One Minute to Zero | Tay Garnett | — | — |
| One Missed Call | Éric Valette | horror film, ghost film | Japan, Germany, United States |
| One Night | Lucas Belvaux | drama film | France, Belgium |
| One Night in Heaven | — | — | Greece |
| One Night in Lisbon | Edward H. Griffith | — | — |
 One Night of Love | Victor Schertzinger | musical film | United States |
| One Nite in Mongkok | Derek Yee | drama film, crime film | Hong Kong |
| One of Our Dinosaurs Is Missing | Robert Stevenson | comedy film, neo-noir | United Kingdom, United States |
| One of the Best | T. Hayes Hunter | — | — |
| One on Romance | Edwin Middleton | — | — |
| One Piece Film: Red | Gorō Taniguchi | fantasy film, comedy film, action film, adventure film | Japan |
| One Piece Film: Strong World | Munehisa Sakai | fantasy film, action film, adventure film | Japan |
| One Piece Film: Z | Tatsuya Nagamine | fantasy film, action film, adventure film | Japan |
| One Piece The Movie: Dead End no Bōken | Kōnosuke Uda | 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 Stolen Night | Scott R. Dunlap | — | — |
| One Thing She Doesn't Have | — | romance film, erotic film | South Korea |
| One Too Many on Board | Gerhard Lamprecht | drama film | Germany |
| One Way Street | Hugo Fregonese | drama film, film noir, crime film | United States |
| One Way Street | John Francis Dillon | — | — |
| One Way Ticket | Herbert Biberman | drama film | United States |
 One Wonderful Night | E. H. Calvert | — | — |
| One, But a Lion! | Gustaf Molander | romantic comedy | Sweden |
 One, Two, Three | Billy Wilder | comedy film | United States |
| One-Hand Clapping | — | drama film, comedy film | Denmark |
| Onibi | Yasuki Chiba | — | Japan |
| Online Murder | Masoud Abparvar | horror film, crime film | Iran |
| Only "Old Men" Are Going Into Battle | Leonid Bykov | war film, musical film, comedy drama | Soviet Union |
| Only Clouds Move the Stars | Torun Lian | drama film, family film | Norway |
| Only God Sees Me | Bruno Podalydès | comedy film | France |
| Only the Strong | Sheldon Lettich | coming-of-age film, martial arts film, action film | United States |
| Only the Wind Knows the Answer | Alfred Vohrer | romance film, drama film, action film | France, Germany |
| Only You | Norman Jewison | coming-of-age film, romantic comedy film | United States, Italy |
| Only You | Jonathan Elbers | romance film | Netherlands |
| Only You | Betty Thomas | romantic comedy | United States |
| Only You | Yevgeny Sherstobitov | musical film | Soviet Union |
| Onna no Hosomichi: Nureta Kaikyo | — | drama film, erotic film | Japan |
| Onni etsii asuntoa | Thure Bahne | comedy film | Finland |
| Onsen jōwa: Yubune de momi gaeri | Tetsuya Takehora | pink film | Japan |
| Onward | Dan Scanlon | fantasy film | United States |
| Onward Christian Soldiers | Rex Wilson | — | — |
| Ooh… You Are Awful | Cliff Owen | independent film | United Kingdom |
| Oore-niwon | Yomi Ogunmola | — | Nigeria |
| Oosaravelli | Surender Reddy | comedy film, action film | India |
| Ooyala | S. V. Krishna Reddy | — | India |
| Op med hodet! | Tancred Ibsen | comedy film | Norway |
| Opa Cor | Peter Verhage, Martin van Waardenberg | comedy film | Netherlands |
| Open All Night | Paul Bern | — | — |
| Open City | Lee Sang-ki | drama film, action film, neo-noir, crime film | South Korea |
| Open Hearts | Susanne Bier | romance film, drama film | Denmark |
| Open Season | Antonin Fourlon, Frédéric Forestier | comedy film | France, Belgium |
| Open Season: Scared Silly | David Feiss | family film, comedy film, werewolf film, buddy film | United States |
| Open Water | Chris Kentis | natural horror film, psychological horror film, psychological thriller film, suspense film, drama film, survival film, horror film, thriller film, adventure film, independent film, psychological drama film, disaster film | United States |
 Opera | Dario Argento | psychological horror film, psychological thriller film, suspense film, crime drama film, mystery film, drama film, giallo, crime thriller film, horror film, thriller film, slasher film, crime film | United States, Italy |
| Operasjon V for vanvidd | Rolf Clemens | crime film | Norway |
| Operation Mekong | Dante Lam | action film, adventure film, crime film | People's Republic of China, Hong Kong |
 Operation Pacific | George Waggner | war film | United States |
| Operation Red Sea | Dante Lam | adventure film, war film, action thriller | People's Republic of China, Hong Kong |
| Operator 13 | Richard Boleslawski | romance film, drama film, spy film, war film | United States |
| Ophelia will arrive a bit later | Lou Scamble, Charles Massicote | fiction | Canada |
| Opium and the Kung-Fu Master | Tong Gai | martial arts film, thriller film | Hong Kong |
| Opowiesc atlantycka | Wanda Jakubowska | — | Poland |
| Oppenheimer | — | drama film, historical film, thriller film, biographical film, epic film | United Kingdom, United States |
 Or | Keren Yedaya | drama film | France, Israel |
| Orange | Kōjirō Hashimoto | drama film, speculative fiction film | Japan |
| Orange County | Jake Kasdan | coming-of-age film, teen film, comedy film | United States |
| Orangerie | Benoît Majerus, Anne Schiltz | documentary film | Luxembourg |
| Orchestra Wives | Archie Mayo | musical film | United States |
| Orchids and Ermine | Alfred Santell | — | — |
| Ordinary People | Robert Redford | drama film | United States |
| Ordinary Person | Aleksandr Stolbov | comedy film | Soviet Union |
| Ore | — | — | Nigeria |
| Orgy | Kōji Wakamatsu | erotic film | Japan |
| Orient Express | Wilhelm Thiele | — | — |
| Origami | Patrick Demers | fiction film, drama film | Canada |
| Origin: Spirits of the Past | Keiichi Sugiyama | post-apocalyptic film, science fiction film, science fiction anime and manga | Japan |
| Orlando | Sally Potter | drama film, fantasy film, LGBTQ-related film | France, United Kingdom, Russia, Italy, Netherlands |
| Orphans | Peter Mullan | comedy drama | United Kingdom |
| Oru Maravathoor Kanavu | Lal Jose | comedy drama | India |
| Oru Veedu Iru Vasal | K. Balachander | — | India |
| Oryu's Passion: Bondage Skin | — | pink film | Japan |
| Os fenómenos | Alfonso Zarauza | drama film | Spain |
| Oscar and Lucinda | Gillian Armstrong | romance film, drama film | United Kingdom, United States, Australia |
| Osen, Chertanovo... | Igor Talankin | drama film | Soviet Union |
| Osenniie svadby | Boris Yashin | drama film | Soviet Union |
| Oshidori kenkagasa | Ryō Hagiwara | — | — |
| Osman Pazarlama | Togan Gökbakar | comedy film | Turkey |
| Osmanlı Kartalı | Osman F. Seden | historical film | Turkey |
| Osobykh primet net | Anatoly Bobrovsky | drama film | Soviet Union, Polish People's Republic |
 Ostatni świadek | Jan Batory | thriller film | Poland |
| Osvobození Prahy | Otakar Vávra | drama film, historical film, war film | East Germany, Germany, Czechoslovakia |
| Otaraant Kvrivi | Mikheil Chiaureli | — | — |
 Other Men's Daughters | Carl Harbaugh | — | — |
| Other Men's Women | William A. Wellman | — | — |
| Otpusk za svoy schyot | Viktor Titov, János Bujtás | comedy film | Soviet Union, Hungary |
| Otrazheniye v zerkale | Svetlana Proskurina | drama film | Russia |
| Otryad | Aleksei Simonov | drama film, war film | Soviet Union |
| Our Enemy — The Japanese | — | — | — |
| Our Erika | German Golub | sport film, biographical film | Estonia |
| Our Heart | Aleksandr Stolper | — | — |
| Our Huge Adventure | Olexa Hewryk | fantasy film, children's film | United States |
 Our Lady of the Turks | Carmelo Bene | drama film | Italy |
 Our Little Sister | Hirokazu Kore-eda | drama film, family film | Japan |
| Our Miss Fred | Bob Kellett | LGBTQ-related film | United Kingdom |
| Our Mother's House | Jack Clayton | drama film | United Kingdom |
| Our Russia. The Balls of Fate | Gleb Orlov | comedy film | Russia |
| Our Russian Front | Joris Ivens | — | — |
| Our Song | Erdenebatyn Oyun | — | Mongolian People's Republic |
| Our Summer With André | Claude Fournier | documentary film | Canada |
| Our Time Will Come | Ann Hui | drama film, historical film, spy film, war film | People's Republic of China, Hong Kong |
| Our Times | Yu Shan Chen | romance film | Taiwan |
| Out of Bounds | Richard Tuggle | action film, crime film | United States |
 Out of the Past | Jacques Tourneur | drama film, film noir, crime film | United States |
 Out of the Ruins | John Francis Dillon | — | — |
| Out of the Shadow | Émile Chautard | — | — |
 Outcast | Chester Withey | — | — |
| Outcast of the Islands | Carol Reed | drama film | United Kingdom |
| Outdoors | Asaf Saban | drama film | Israel |
| Outlaw King | David Mackenzie | drama film, historical film, action film, adventure film, medieval film, biographical film | United Kingdom, United States |
| Outrage | Takeshi Kitano | drama film, action film, crime film | Japan |
| Outside Providence | Michael Corrente | romance film, drama film, romantic comedy | United States |
| Outside the Law | Tod Browning | crime film | United States |
| Outsider | Andrej Košak | drama film | Slovenia |
 Outward Bound | Robert Milton | drama film, fantasy film | United States |
| Over the Border | Ahn Pan-seok | romance film, drama film | South Korea |
| Over the Garden Wall | John E. Blakeley | comedy film | United Kingdom |
| Over the Hedge | Karey Kirkpatrick, Tim Johnson | family film, comedy film, Greatest Movie Hits, adventure film, science fiction film, heist film, buddy cop film, buddy film | United States |
| Over the Hill | Henry King | drama film | United States |
| Over Your Dead Body | Jorma Taccone | thriller film, action comedy film | United States |
| Overboard | Bob Fisher, Rob Greenberg | romance film, comedy film | United States, Mexico |
| Overland Telegraph | Lesley Selander | Western film | United States |
| Ozhog | Gennady Glagolev | crime drama film | Soviet Union |
| Özlem…Düne, Bugüne, Yarına | Tülay Eratalay | — | Turkey |
| Ọ̀wánrán iná | ʼṢọla Kunlerẹ | — | Nigeria |
| Øyeblikket | Sverre Udnæs | drama film | Norway |