| O chyom govoryat muzhchiny. Prostye udovolstviya | — | comedy film | Russia |
| O chyom molchat devushki | Karen Oganesyan | comedy film | Russia |
| O gamos tis koris mou | Nikos Koutelidakis | comedy film | Greece |
| O Que Resta | — | drama film | Brazil |
| O Stratis parastratise | Kostas Karagiannis | comedy film | Greece |
| O thanatos tha xanarthi | Errikos Thalassinos | drama film | Greece |
| O.C. and Stiggs | Robert Altman | teen film | United States |
| O.K. ... Laliberté | Marcel Carrière | comedy drama | Canada |
| Oath of Timur | Aleksandra Khokhlova | — | — |
| Obaba | Montxo Armendáriz | drama film | Germany, Spain |
| Obcy w lesie | Sylwester Szyszko | — | Poland |
| Obhishopto Nighty | Birsa Dasgupta | comedy film, thriller film | India |
| Obscene temptation of wife | Lee Ji-eun | erotic film | South Korea |
| Ocean Waves | Tomomi Mochizuki | romance film | Japan |
| Ocean's 8 | Gary Ross | comedy film, action film, thriller film, heist film, female buddy film, crime film | United States |
| Ocean's Twelve | Steven Soderbergh | mystery film, comedy film, action film, detective film, heist film | United States |
| October | Shoojit Sircar | slice of life, romantic drama | India |
| October Baby | Andrew Erwin, Jon Erwin | drama film | United States |
| Octobre | Pierre Falardeau | drama film | Canada |
| Oculus | Mike Flanagan | horror film, ghost film, psychological horror fiction, supernatural fiction | United States |
| Oczy uroczne | Piotr Szulkin | horror film | Poland |
| Odds Against Tomorrow | Robert Wise | drama film, film noir, heist film, crime film | United States |
| Odoru ryū kyūjō | Yasushi Sasaki | — | — |
| Odysseus und die Sterne | Ludvík Ráža | mystery film, family film, fantasy film, science fiction film | Czechoslovakia |
| Oedipus Rex | Pier Paolo Pasolini | drama film | Italy |
| Oeil pour oeil | André Cayatte | drama film | France, Italy |
| Of Human Hearts | Clarence Brown | — | — |
| Of Love and Shadows | Betty Kaplan | drama film | United States, Argentina |
| Of Mice and Men | Gary Sinise | drama film, historical drama | United States |
| Offered for Singles | Samson Samsonov | romance film, comedy drama | Soviet Union |
| Office Lady Rope Slave | — | pink film, pornographic film | Japan |
| Officer with a Rose | Dejan Šorak | melodrama | Yugoslavia |
| Officers | Vladimir Rogovoy | romance film, drama film, historical film, war film | Soviet Union |
| Offline: Are You Ready for the Next Level? | Florian Schnell | comedy film, adventure film | Germany |
| Offside | Serdar Akar | association football film, comedy drama | Turkey |
| Oh Baby | Cassandra Massardi | drama film | Indonesia |
| Oh dolci baci e languide carezze | Mino Guerrini | comedy film, sex film | Italy |
| Oh! Heavenly Dog | Joe Camp | fantasy film, comedy film | United States |
| Oh, For a Man! | Hamilton MacFadden | musical film, romantic comedy | United States |
| Oh, Kay! | Mervyn LeRoy | — | — |
| Oh, Serafina! | Alberto Lattuada | comedy film | Italy |
| Oi paranomoi | Nikos Koundouros | drama film | Greece |
| Oilspot and Lipstick | Michael Cedeno | animated film | United States |
| Oiseau de printemps, hirondelle d'hiver | Georges Denola | — | — |
| Oj ne khody, Hrytsu, ta j na vechornytsi | Rostyslav Synko | drama film | Soviet Union |
| Oka Laila Kosam | Vijay Kumar Konda | romance film | India |
| Okashiratsuki | Mikiya Sanada | — | Japan |
| Okean Elzy: Stormwatch | Artem Hryhorian | biographical film, documentary film | Ukraine |
| Okinawa Rendez-vous | Gordon Chan | romantic comedy | Hong Kong |
| Okkadu | Gunasekhar | action film | India |
| Oklahoma Annie | R. G. Springsteen | Western film | United States |
| Oklahoma! | Fred Zinnemann | musical film | United States |
| Okovani soferi | Vladimir Pavlovich | drama film, partisan film | Soviet Union, Yugoslavia |
| Oktyabryukhov and Dekabryukhov | Aleksey Smirnov | — | — |
| Olaf's Frozen Adventure | Kevin Deters, Stevie Wermers | family film, fantasy film, comedy film, Christmas film, adventure film, musical film | United States |
| Old | M. Night Shyamalan | comedy horror film, psychological horror film, suspense film, mystery film, drama film, comedy film, horror film, thriller film, supernatural film, supernatural horror film, psychological drama film | United States |
| Old Home Week | Victor Heerman | — | — |
| Old Isaacs, the Pawnbroker | Wallace McCutcheon, Sr. | — | — |
| Old Khottabych | Gennady Kazansky | — | — |
| Old Letters | Anatolii Ivanov | drama film | Soviet Union |
| Old Mother Riley Detective | Lance Comfort | — | — |
| Old Mother Riley in Business | John Baxter | — | — |
| Old Mother Riley Overseas | Oswald Mitchell | comedy film | United Kingdom |
| Old Oklahoma Plains | William Witney | Western film | United States |
| Old Overland Trail | William Witney | Western film | United States |
| Old Walls | Viktor Tregubovich | romance film, drama film | Soviet Union |
| Oldboy | Spike Lee | mystery film, drama film, crime film | United States |
| Olga | Markku Onttonen | drama film | Finland |
| Oliver! | Carol Reed | drama film, musical film, crime film | United Kingdom |
| Olli’s Apprenticeship | Teuvo Puro | — | — |
| Olsen Gang jr. Master Thief tax | Arne Lindtner Næss | comedy film | Norway |
| Olsenbanden | Knut Bohwim | crime comedy film, action comedy film | Norway |
| Olsenbanden og Data-Harry sprenger verdensbanken | Knut Bohwim | crime comedy film | Norway |
| Olsenbanden og Dynamitt-Harry går amok | Knut Bohwim | crime comedy film | Norway |
| Olsenbanden tar gull | Knut Bohwim | crime comedy film | Norway |
| Omar Khayyam | William Dieterle | biographical film | United States |
| Omega, Omega | Gervasio Iglesias Macías | documentary film | Spain |
| Omena putoaa... | Valentin Vaala | — | — |
| OMG – Oh My God! | Umesh Shukla | fantasy film, trial film, comedy drama | India |
| 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 an Island with You | Richard Thorpe | aqua-musical, musical film, romantic comedy | United States |
| On Approval | Clive Brook | — | — |
| On Chesil Beach | Dominic Cooke | drama film, melodrama | United Kingdom |
| On Golden Pond | Mark Rydell | romance film, drama film | United States |
| On My Way | Emmanuelle Bercot | drama film, comedy film, road movie | France |
| On Secret Service | Arthur B. Woods | — | — |
| 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 day of the holiday | Pyotr Todorovsky | drama film | Soviet Union |
| On the Loose | Charles Lederer | — | — |
| On the Night of the Lunar Eclipse (film) | Baras Khalzanov | historical film | Soviet Union |
| On the Occasion of Remembering the Turning Gate | Hong Sang-soo | drama film | South Korea |
| On the Old Spanish Trail | William Witney | — | — |
| On the Quiet | Chester Withey | — | — |
| On the Riviera | Walter Lang | musical film, romantic comedy | United States |
| On the Run | Alfred Cheung | action film, gangster film | Hong Kong |
| On the Silver Globe | Andrzej Żuławski | arthouse science fiction film, drama film, dystopian film, science fiction film | Poland |
| On the Steppe | Boriss Bunejev | — | — |
| On the Sunny Side | Ralf Kirsten | musical film | East Germany |
| On the Threshold of Space | Robert D. Webb | — | — |
| On the Waterfront | Elia Kazan | drama film, thriller film, crime film | United States |
| On the Way to Berlin | Mikhail Yershov | war film | Soviet Union |
| On Thursday and Never Again | Anatoly Efros | romance film, drama film | Soviet Union |
| On Wings of Love | Toshio Sugie | — | — |
| On Your Mark | Hayao Miyazaki | science fiction anime and manga | Japan |
| On Ze Boulevard | Harry F. Millarde | — | — |
| Once | John Carney | musical film | Ireland |
| Once Lied | Vladimir Bortko | romance film, drama film | Soviet Union |
| Once Upon a Dog | Eduard Nazarov | comedy film, children's film, adventure film | Soviet Union |
| Once Upon a Forest | Luc Jacquet | documentary film | France |
| Once Upon a Honeymoon | Leo McCarey | comedy drama, romantic comedy | United States |
| Once Upon a Horse... | Hal Kanter | Western film | United States |
| Once Upon a Time in a Battlefield | Lee Joon-ik | drama film, medieval film, war film | South Korea |
| Once Upon a Time in China | Tsui Hark | martial arts film, action film, biographical film | Hong Kong |
| Once Upon a Time in China II | Tsui Hark | martial arts film, action 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 the Desert | Andrei Kravchuk | drama film, war film | Russia, Syria |
| Once Upon a Time in the Middle East | Wen Muye | drama film, war 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 Upon My Mother | Ken Scott | comedy film, comedy drama | France, Canada |
| 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 and Eight | Zhang Junzhao | war film | People's Republic of China |
| One Careful Owner | — | comedy drama | Spain |
| One Crazy Summer | Savage Steve Holland | romantic comedy film | United States |
| One Day | Lone Scherfig | romance film, drama film | United Kingdom, United States |
| One Day in September | Kevin Macdonald | documentary film, crime film | United Kingdom, Germany, Switzerland |
| One Desire | Jerry Hopper | romance film, drama film | United States |
| One Direction: This Is Us | Morgan Spurlock | documentary film | United Kingdom, United States |
| One Exciting Night | Walter Forde | — | — |
| One Exciting Night | D. W. Griffith | — | — |
| One Fine Spring Day | Hur Jin-ho | romance film | South Korea |
| One Foot in Heaven | Irving Rapper | — | — |
| One for the Road | Nattawut Poonpiriya | drama film | People's Republic of China, Hong Kong, Thailand |
| One for the Road | Philippe Godeau | drama film | France |
| One Good Turn | Arthur Maude | comedy film | United Kingdom |
| One Hundred Steps | Marco Tullio Giordana | drama film, biographical film | Italy |
| One in a Million | Sidney Lanfield | musical film, romantic comedy | United States |
| One Life and Two Trails | Alberto Arvelo | drama film | Venezuela |
| One Little Indian | Bernard McEveety | comedy film, Western film | United States |
| One Man's Journey | John S. Robertson | — | — |
| One Minute to Zero | Tay Garnett | — | — |
| One Missed Call | Takashi Miike | horror film, ghost film | Japan |
| One More Tomorrow | Peter Godfrey | comedy film | United States |
| One Night | — | — | — |
| One Night in Heaven | — | — | Greece |
| One Night Stand | Allan King | drama film, thriller film | Canada |
| One Night Stand | Marquise Lepage | fiction film, romantic comedy | Canada |
| One of the Best | T. Hayes Hunter | — | — |
| One of the People | Dejidiin Jigjid | — | Mongolian People's Republic |
| One on Romance | Edwin Middleton | — | — |
| One Piece Film: Gold | Miyamoto Hiroaki | fantasy film, action film, adventure film | Japan |
| One Piece Film: Strong World | Munehisa Sakai | fantasy film, action film, adventure film | Japan |
| 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: Stampede | Takashi Ōtsuka | fantasy film, action film, anime film, adventure film | Japan |
| One Silver Piece | Jaroslav Balík | drama film | Czechoslovakia |
| One Sunday Afternoon | Stephen Roberts | — | — |
| One Thing She Doesn't Have | — | romance film, erotic film | South Korea |
| One True Love | Mark Osepyan | drama film | Soviet Union |
| One Way Ticket | Herbert Biberman | drama film | United States |
| One Year to Live | Irving Cummings | — | — |
| One Year, One Night | Isaki Lacuesta | drama film | France, Spain |
| One, Two, Three | Billy Wilder | comedy film | United States |
| Onek Sadher Moyna | Jakir Hossain Raju | romance film | Bangladesh |
| Ong Bak 2 | Panna Rittikrai, Tony Jaa | martial arts film | Thailand |
| Online Murder | Masoud Abparvar | horror film, crime film | Iran |
| Only a Servant | Erik Lund | — | — |
| Only Angels Have Wings | Howard Hawks | drama film | United States |
| Only Clouds Move the Stars | Torun Lian | drama film, family film | Norway |
| Only the Brave | Joseph Kosinski | drama film, action film, biographical film | United States |
| Only You | Norman Jewison | coming-of-age film, romantic comedy film | United States, Italy |
| Only You | Betty Thomas | romantic comedy | United States |
| Onna Keirin-ō | Kiyoshi Komori | — | — |
| Onna kyōshi: yogoreta hōkago | Kichitarō Negishi | pink film, drama film | Japan |
| Onnanam Kunnil Oradi Kunnil | Priyadarshan | — | India |
| Onsen jōwa: Yubune de momi gaeri | Tetsuya Takehora | pink film | Japan |
| Open All Night | Paul Bern | — | — |
| Open Future | Petter Vennerød, Svend Wam | drama film | Norway |
| Open Hearts | Susanne Bier | romance film, drama film | Denmark |
| Open Places | W. S. Van Dyke | — | — |
| Open Range | Clifford Smith | — | — |
| 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 |
| 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 |
| Operasi Pesta Copet | Edy Khemod | comedy film, musical film, crime film | Indonesia |
| Operasjon Løvsprett | Knut Andersen | comedy film | Norway |
| Operation Atlantis | Domenico Paolella | adventure film | Italy |
| Operation Avalanche | Matt Johnson | thriller film | Canada, United States |
| Operation Cupid | Charles Saunders | comedy film | United Kingdom |
| Operation Delta Force 3: Clear Target | Mark Roper | action film | United States |
| Operation Dumbo Drop | Simon Wincer | comedy film | United States |
| Operation Petticoat | Blake Edwards | comedy film, war film | United States |
| Operation Y and Other Shurik's Adventures | Leonid Gaidai | comedy film, anthology film | Soviet Union |
| Opettajatar seikkailee | Aarne Tarkas | comedy film | Finland |
| Ophelia will arrive a bit later | Lou Scamble, Charles Massicote | fiction | Canada |
| Opposites Attract | Max Croci | comedy film | Italy |
| Orange | Bhaskar | romantic comedy | India |
| 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 |
| Ordinary Victories | Laurent Tuel | comedy drama | France |
| Orensanz | Rocío Mesa | documentary film | Spain |
| Orgy : The XXX championship | Hervé Bodilis, Paul Thomas | pornographic film | France |
| Orient Express | Victor Tourjansky | — | — |
| Orisa | Odunlade Jonathan Adekola | drama film | Nigeria |
| Orphans | Peter Mullan | comedy drama | United Kingdom |
| Orphans of the Storm | D. W. Griffith | — | — |
| Orphans of the Street | John H. Auer | drama film | United States |
| Orpheus in der Unterwelt | — | — | — |
| Oru Kidayin Karunai Manu | Suresh Sangaiah | comedy drama | India |
| Oru Maravathoor Kanavu | Lal Jose | comedy drama | India |
| Oru Sundariyude Katha | Thoppil Bhasi | — | India |
| Oscar | Édouard Molinaro | comedy film | France |
| Osen, Chertanovo... | Igor Talankin | drama film | Soviet Union |
| Oshi, Mankai | Hidekazu Takahara | pink film | Japan |
| Osiris | William Kaufman | action film, science fiction film | United States |
| Osmosis Jones | Peter Farrelly, Piet Kroon, Tom Sito, Bobby Farrelly | comedy film, action film, children's film, buddy cop film, buddy film | United States |
| Ot zari do zari | Gabriel Egiazarov | drama film | Soviet Union |
| Otaraant Kvrivi | Mikheil Chiaureli | — | — |
| Otello | — | — | Soviet Union |
| Otello | Arrigo Frusta | — | — |
| Other Men's Women | William A. Wellman | — | — |
| Other People's Relatives | Mikhail Schweitzer | — | — |
| Otis | Tony Krantz | comedy horror | United States |
| Otpusk za svoy schyot | Viktor Titov, János Bujtás | comedy film | Soviet Union, Hungary |
| Our Betters | George Cukor | comedy film | United States |
| Our Blushing Brides | Harry Beaumont | romance film, drama film, comedy drama, romantic comedy | United States |
| Our Brothers | Rachid Bouchareb | historical drama | France |
| Our correspondent | Anatoliy Granik | drama film | Soviet Union |
| Our Erika | German Golub | sport film, biographical film | Estonia |
| Our Friend | Gabriela Cowperthwaite | drama film | United States |
| Our Futures | Rémi Bezançon | buddy film, comedy drama | France |
| Our God's Brother | Krzysztof Zanussi | biographical film | Poland, Italy |
| Our Idiot Brother | Jesse Peretz | drama film, comedy film, LGBTQ-related film | United States |
| Our Lips Are Sealed | Craig Shapiro | comedy film | United States |
| 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 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 |
| Out All Night | Sam Taylor | comedy film | United States |
| Out of Africa | Sydney Pollack | romance film, drama film, adventure film, biographical film | United States |
| Out Of Our System | Dan Humes, Rhiannon Humes, Seth Gamble | drama film, pornographic film | Canada |
| Out of Scale | Jack Hannah | — | United States |
| Out of the Furnace | Scott Cooper | drama film, thriller film, prison film | United States |
| Out of the Ruins | John Francis Dillon | — | — |
| Out of This World | Hal Walker | romantic comedy film | United States |
| Out West with the Peppers | Charles Barton | comedy film | United States |
| Outland | Peter Hyams | action film, adventure film, science fiction film | United Kingdom |
| Outlaw King | David Mackenzie | drama film, historical film, action film, adventure film, medieval film, biographical film | United Kingdom, United States |
| Outlaws of Sonora | George Sherman | — | — |
| Outside In | Tamara Munzner | — | United States |
| Outside Providence | Michael Corrente | romance film, drama film, romantic comedy | United States |
| Outside the Wall | Crane Wilbur | drama film, film noir, crime film | United States |
| Ovejas negras | José María Carreño Bermúdez | black comedy | Spain |
| Over the Hill | Henry King | drama film | United States |
| Overboard | Bob Fisher, Rob Greenberg | romance film, comedy film | United States, Mexico |
| Overdose | Olivier Marchal | action film, police film, thriller film | France |
| Overexposed | Larry Brand | thriller film | United States |
| Overheard | Alan Mak, Felix Chong | thriller film, crime film | Hong Kong |
| Overland Stage Raiders | George Sherman | Western film | United States |
| Overseas | Brigitte Roüan | drama film | France |
| Ovunque sei | Michele Placido | drama film | Italy |
| Oz the Great and Powerful | Sam Raimi | family film, fantasy film, comedy film, adventure film | United States |
| Ozhog | Gennady Glagolev | crime drama film | Soviet Union |
| Oʻtgan kunlar | Yoʻldosh Aʼzamov | drama film, historical film | Soviet Union |
| Özlem…Düne, Bugüne, Yarına | Tülay Eratalay | — | Turkey |
| Ōoku Maruhi Monogatari | Sadao Nakajima | erotic film | Japan |