| O Entertainment | United States | 1990 | 2013 | 3 |
| O2 Films | Brazil | — | — | 3 |
| O3 Medya | — | — | — | 1 |
| Oakhurst Productions | United States | — | — | 2 |
| Oakshire Productions | United Kingdom | — | — | 1 |
| Oberon Cinematogràfica | Spain | 1990 | — | 1 |
| Oberon Media | United States | 2003 | — | 2 |
| Objectif 9 | Canada | — | — | 1 |
| Objectiv Filmstudio | Hungary | — | — | 1 |
| Ocean Entertainment | Canada | — | — | — |
| Oceania Produzioni Internazionali Cinematografiche | Italy | — | — | 1 |
| Oceanic Preservation Society | United States | 2005 | — | 1 |
| OCN | South Korea | 1995 | — | 6 |
| OCS | France | January 7, 1991 | — | 1 |
| October Films | United States | 1991 | 2002 | 9 |
| OddLot Entertainment | United States | 2001 | 2015 | 1 |
| Odeon | Greece | — | — | 1 |
| Odeon Film | Germany | 1998 | — | — |
| Odesa Film Studio | Ukraine | 1919 | — | 128 |
| Odessa Films | France | — | — | 5 |
| Odessa Filmworks | — | — | — | 1 |
| Odolttogi (Animation Studio) | South Korea | April 1997 | — | 1 |
| Odyssey Entertainment | — | — | — | 1 |
| Office de Radio et Télévision des Comores | — | December 14, 2015 | — | — |
| Office de radiodiffusion télévision française | France | 1964 | 1974 | 3 |
| OFFICE TO ONE | Japan | June 5, 1963 | — | — |
| Official Credit Institute | Spain | 1962 | — | 3 |
| OffSide | Italy | — | — | 2 |
| OGN | South Korea | July 24, 2000 | — | — |
| Ognon Pictures | France | — | — | 3 |
| Ogun State Television | Nigeria | 1981 | — | 2 |
| Okko | Russia | 2011 | — | 1 |
| Okko Production | Czech Republic | — | — | 1 |
| Oktober | Finland | June 4, 2004 | — | 2 |
| OLM, Inc. | Japan | June 1994 | — | 31 |
| Olympic | — | 1962 | — | 1 |
| Om Films | United States | 2006 | — | — |
| Ombetja Yehinga Organisation | Namibia | 2001 | — | 1 |
| Ombra Films | Spain | — | — | 3 |
| Omega Film & Television | Sweden | — | — | 3 |
| Omega Film GmbH | Germany | — | — | 1 |
| Omnia Film | Germany | — | — | 1 |
| Omnifilm Entertainment | Canada | — | — | — |
| Omroep MAX | Netherlands | 2002 | — | 1 |
| On the Day Productions | United States | — | — | 3 |
| One Astor Plaza | United States | 1972 | — | 1 |
| ONE Championship | Singapore | July 14, 2011 | — | 1 |
| One Cool Film Production Limited | — | 2013 | — | 3 |
| One Fine Day Films | Germany | 2008 | — | 1 |
| One Hundred Years of Film | — | 1999 | — | 14 |
| One Race Films | United States | 1995 | — | 8 |
| One's Youth | Japan | 2015 | 2024 | — |
| Onfilm | Estonia | 1996 | — | 1 |
| ONO | Spain | September 29, 1998 | 2018 | 2 |
| Onyx Collective | United States | May 17, 2021 | — | — |
| OP Eiga | Japan | June 1947 | — | 114 |
| Open de España | Spain | 1912 | — | 1 |
| Open Road Flims | United States | 2011 | — | 4 |
| Optimystix Entertainment | — | 2000 | — | 1 |
| Opus Film | Poland | 1991 | — | 4 |
| Orange | France | 1988 | — | 1 |
| Orange Cinéma Séries | France | November 13, 2008 | July 3, 2024 | 1 |
| Orange Sky Golden Harvest | People's Republic of China | 1970 | — | 146 |
| Orange Studio | — | 2007 | — | 20 |
| Orange Studio | France | October 22, 2001 | — | 1 |
| Orange Television Network | United States | 2005 | — | — |
| Orbis, Rhineland-Palatinate | Germany | — | — | 1 |
| Oria Films | Spain | 1999 | — | 4 |
| Oriental Film | — | 1940 | — | 1 |
| Origen P.C. | Spain | — | — | 1 |
| Origin Animation | People's Republic of China | July 14, 2010 | — | 1 |
| Origin Pictures | United Kingdom | 2008 | — | 2 |
| Original Film | United States | 1997 | — | 59 |
| Original Productions | United States | 1999 | — | — |
| Orion Classics | United States | 1982 | — | 1 |
| Orion Pictures | United States | 1978 | — | 87 |
| Orisono | Switzerland | 2020 | — | 1 |
| Orlando Film Festival | United States | 2005 | — | 1 |
| Ornis Films | Spain | 1969 | — | — |
| Orona/Stevens | United States | — | — | 1 |
| Osakond | Estonia | 2004 | — | 1 |
| Oscar Film | Pahlavi Iran | — | — | 18 |
| Oscilloscope | — | 2008 | — | 5 |
| Oslo Film | Norway | 1946 | — | 1 |
| Oslo Talefilm | Norway | — | — | 3 |
| Ostankino | Russia | December 27, 1991 | — | — |
| Ostdeutscher Rundfunk Brandenburg | Germany | October 12, 1991 | April 30, 2003 | 2 |
| Ostlicht Filmproduktion | Germany | 2009 | — | 2 |
| Otomatic | Belgium | — | — | 1 |
| Ouille Productions | France | 1996 | — | 1 |
| Outerbanks Entertainment | United States | June 29, 1995 | — | 2 |
| Outlaw Productions | United States | — | — | 8 |
| Outre-Mer 1ère | France | September 14, 1954 | — | 1 |
| Outside Films | France | — | — | 1 |
| Outspoken Media | — | 2004 | — | 1 |
| Overbrook Entertainment | United States | 1998 | — | 20 |
| Overseas Chinese Films | British Hong Kong | — | — | 1 |
| Overture Films | United States | 2006 | 2010 | 3 |
| Ovídeo TV | Spain | — | — | 3 |
| Owesen-film | Norway | — | — | 3 |
| Owj Arts and Media Organization | Iran | 2011 | — | 5 |
| Oxford Films | United Kingdom | — | — | 1 |
| Oxford Scientific Films | United Kingdom | 1968 | — | — |
| OXYBOT | Japan | December 2004 | — | 1 |
| Oy Nordisk Film Ab | Finland | August 30, 1984 | — | 1 |
| OÜ Polarfilm | Estonia | 1998 | — | — |
| Õ-Fraktsioon | Estonia | May 14, 2003 | — | 1 |
| Ö-Filmproduktion Löprich & Schlösser | Germany | — | — | 2 |
| Österreichischer Rundfunk | Austria | May 19, 1953 | — | 11 |
| Özen Film | Turkey | — | — | 3 |