

| Acronym | Sense | Language | Topics | 
|---|---|---|---|
| NVAO | Nederlands-Vlaamse Accreditatieorganisatie (www.nvao.net) | In Dutch | → Education | 
| NVAV | Nederlandse Vereniging van Amateur Vliegtuigbouwers (www.nvav.nl) | In Dutch | → Aeronautics, aircraft → Netherlands | 
| NVBS | Nederlandse Vereniging van Belangstellenden in het Spoor- en tramwegwezen (www.nvbs.com) | In Dutch | → Rail transport engineering | 
| NVC | Netterdense Voetbal Club | In Dutch | → Football and rugby | 
| NVC | Naarden De Vesting Combinatie | In Dutch | → Sport, physical exercises | 
| NVCA | National Venture Capital Association (www.nvca.org) | In English | → Associations → 33676 | 
| NVDO | Nederlandse Video Detaillisten Vereniging | In Dutch | → Netherlands | 
| NVEOL | Night Vision and Electro-Optical Laboratory | In English | → Research institutes | 
| NVEOL | Night Vision and Electronic-Optics Laboratory | In English | → Research institutes → Electronics | 
| NVG | Nederlandse Verbond van Groothandel | In Dutch | → Trade → Netherlands | 
| NVGD | Nederlandse Vereniging van Grammofoonplaten Detailhandelaren | In Dutch | → Music → Trade → Netherlands | 
| NVO | Nevyriausybinė organizacija = ONGs | Organizações Não Governamentais | In Portuguese = NGO | Non-Governmental Organization | In English = NGO | Nichtregierungsorganisation | In German = ANG | Aozadur Nann-Gouarnamantel | In Breton = ONG | Organisation Non Gouvernementale | In French = NRO | Ne-Registara Organizo | In Esperanto = ONG | Organizzazione non governativa | In Italian = LSM | Lembaga Swadaya Masyarakat | In Indonesian = ONG | Organización non gobernamental | In Galician = GKE | Gobernuz Kanpoko Erakunde | In Basque = ONG | Organización no gubernamental | In Spanish = ΜΚΟ | Μη κυβερνητικές οργανώσεις | In Greek = NNO | Nevládní nezisková organizace | In Czech = ONG | Organització no governamental | In Catalan = ННО | Неурядові неприбуткові організації | In Ukrainian = ONG | Organização não governamental | In Portuguese = NGO | Niet-gouvernementele organisatie | In Dutch | In Lithuanian | |
| NVON | Nederlandse Vereniging voor Onderwijs in de Natuurwetenschappen (www.nvon.nl) | In Dutch | → Education → Applied sciences, technology → Netherlands | 
| NVPHBV | Nederlandse Vereniging voor Patroonherkenning en Beeldverwerking | In Dutch | → Graphical processing → Image processing → Netherlands | 
| NVS | Nieuw Vossemeerse Sportvereniging | In Dutch | → Sport, physical exercises | 
| NVTG | Nederlandse Vereniging voor Tropische Geneeskunde | In Dutch | → Medicine → Netherlands | 
| NVvA | Nederlandsche Vereeniging van Antiquaren (www.nvva.nl) | In Dutch | → Associations → Trade → Netherlands | 
| NVvV | Nederlandse Vereniging voor Vlaggenkunde | In Dutch | → Flags, banners → Netherlands | 
| NVVW | Nederlands Verbond van Detailhandelaren in Verf en Wandbekleding | In Dutch | → Trade → Netherlands | 
| NWC | NOAD Wilhelmina Combinatie | In Dutch | → Sport, physical exercises | 
| NWCI | National Women's Council of Ireland (www.nwci.ie) | In English | → Feminism → Republic of Ireland | 
| NWDV | Nordrhein-Westfälischer Dartverband | In German | → Sport, physical exercises | 
| NWP | Netherlands Water Partnership | In English | → Hydrology → Environmental technology, water supply, waste management | 
| NWR | Nationale Winkelraad van MKB-Nederland | In Dutch | → Netherlands | 
| NWR | Natuurwetenschappelijke Raad voor Nederlandsch-Indië | In Dutch | → Research policy → Indonesia | 
| NWVV | Nieuw Weerdinger Voetbal Vereniging | In Dutch | → Football and rugby | 
| NYCAS | New York Conference on Asian Studies | In English | → Congresses → Area studies → United States | 
| NYSAFLT | New York State Association of Foreign Language Teachers (www.nysaflt.org) | In English | → Associations → Education → Language, linguistics, literature → United States | 
| NYSCEDII | New York State Center for Engineering Design and Industrial Innovations (www.nyscedii.buffalo.edu) | In English | → Research policy → Engineering, technology → Drawing and applied arts → United States | 
| NZEA | Nov-Zelanda Esperanto-Asocio (www.esperanto.org.nz) = NZEA | New Zealand Esperanto Association | In English | In Esperanto | → Associations → Artificial languages (linguistics) | 
| NZEA | New Zealand Esperanto Association (www.esperanto.org.nz) = (look above) | In English | → Associations → Artificial languages (linguistics) | 
| NZFA | New Zealand Flag Association | In English | → Associations → Flags, banners | 
| OAB | Oost Arnhemse Boys | In Dutch | → Sport, physical exercises | 
| ÖAD | Österreichischer Austauschdienst (www.oead.ac.at) | In German | → Education → Austria | 
| ÖÄGMM | Österreichische Ärztegesellschaft für Manuelle Medizin (www.manuellemedizin.org) | In German | → Medicine → Austria | 
| OAH | Organization of American Historians (www.oah.org) | In English | → History → United States | 
| ÖAI | Österreichisches Archäologisches Institut (www.oeai.at) | In German | → Research institutes → Archeology → Austria | 
| OAIS | Ohio Association of Independent Schools (www.oais.org) | In English | → Associations → Education → United States | 
| ÖÄK | Österreichische Ärztekammer (www.aerztekammer.at) | In German | → Medicine → Austria | 
| ÖAMTC | Österreichischer Automobil-, Motorrad- und Touring Club (www.oeamtc.at) | In German | → Vehicle engineering → Transport and postal services → Austria | 
| OAPEC | Organization of Arab Petroleum Exporting Countries | In English | → Trade → 665 | 
| OAPI | Organisation Africaine de la Propriété Intellectuelle (www.oapi.wipo.net) = AIPO | African Intellectual Property Organization | In English | In French | → Industrial property → Artistic property → Africa | 
| OAR | Organization for Asian Research | In English | → Research policy | 
| OAR | Ordinul Arhitectilor din România | In Romanian | → Architecture → Romania | 
| ÖAR | Österreichische Arbeitsgemeinschaft für Rehabilitation (www.oear.or.at) | In German | → Associations → Austria | 
| OASIS | Organisation for the Advancement of Structural Information Standard | In English | → Standardization → Data → Networks, communication | 
| OAVT | Ontario Association of Veterinary Technicians (www.oavt.org) | In English | → Associations → Veterinary medicine → Canada | 
| ÖAW | Österreichische Akademie der Wissenschaften (www.oeaw.ac.at) | In German | → Academies → Mathematics and natural sciences → Austria | 
| OB | Onderling Bevriend | In Dutch | → Sport, physical exercises | 
| OBDV | Oberbayerischer Dartverband | In German | → Sport, physical exercises | 
| OBFA | Occupational Benevolent Funds Alliance | In English | → Labour, labour economics | 
| OBG | Oregon Brewers Guild (http://oregonbeer.org) | In English | → Beverage industry | 
| ÖBR | Österreichische Buddhistische Religionsgesellschaft (www.buddhismus-austria.at) | In German | → Buddhism → Austria | 
| OBV | Order Bossche Voetbalclub | In Dutch | → Football and rugby | 
| OBVP | Österreichischer Bundesverband für Psychotherapie (www.psychotherapie.at) | In German | → Psychology → Neurology → Austria | 
| OBW | Ooij's Blauw Wit | In Dutch | → Sport, physical exercises | 
| OCA | Open Content Alliance | In English | → Computer science | 
| OCA | Organisation Combat Anarchiste | In French | → Anarchist organizations | 
| OCAP | Ontario Coalition Against Poverty (www.ocap.ca) | In English | → Economics → Social welfare → Canada | 
| OCCARO | Orange County Council of Amateur Radio Organizations | In English | → Telecommunications | 
| OCDU | Otor-Owhe Community Development Union | In English | → Regional planning | 
| OCDU | Oleh Community Development Union | In English | → Regional planning | 
| ÖCG | Österreichische Computer Gesellschaft (www.ocg.at) | In German | → Computer science → Austria | 
| OCIM | Office de Coopération et d'Information Muséographiques | In French | → Museums | 
| OCM | Organisation Civile et Militaire | In French | → History | 
| OCM | Organisations Communes des Marchés | In French | → Economics | 
| OCOGs | Organising Committees for the Olympic Games | In English | → Sport, physical exercises | 
| OCQ | Ordre des Chimistes du Québec | In French | → Chemistry → Chemical technology → Canada | 
| OCQ | Ordre des Chiropraticiens du Québec | In French | → Occult sciences → Canada | 
| OCS | Olympic Club de Safi (www.ocs.ma) | In French | → Football and rugby → Morocco | 
| ODB | Ons Doel Bereikt | In Dutch | → Sport, physical exercises | 
| ODC | Overwinning Door Combinatie | In Dutch | → Sport, physical exercises | 
| ODE | Overwinnen Door Eendracht | In Dutch | → Sport, physical exercises | 
| ÖDG | Österreichische Diabetes-Gesellschaft (www.oedg.org) | In German | → Physiology → Pathology → Austria | 
| ODI | Ontspanning Door Inspanning | In Dutch | → Sport, physical exercises | 
| ODIN | Ons Doel Is Nuttig | In Dutch | → Sport, physical exercises | 
| ODIO | Ons Doel Is Overwinnen | In Dutch | → Sport, physical exercises | 
| ODIZ | Ons Doel Is Zegevieren | In Dutch | → Sport, physical exercises | 
| ODMG | Object Database Management Group | In English | → Data | 
| ODO | Overwinnen Door Oefening | In Dutch | → Sport, physical exercises | 
| ODO | Oefening Doet Overwinnen | In Dutch | → Sport, physical exercises | 
| ODS | Oefening Doet Slagen | In Dutch | → Sport, physical exercises | 
| ODSEF | Observatoire Démographique et Statistique de l'Espace Francophone | In French | → Demography → Statistics | 
| ODUPA | Organización de Deporte Universitario Panamericano | In Spanish | → Higher education, universities → Sport, physical exercises | 
| ODV | Ontspanning Door Voetbal | In Dutch | → Football and rugby | 
| OeAV | Österreichischer Alpenverein (www.alpenverein.at) | In German | → Austria | 
| OECI | Organization of European Cancer Institutes (http://https://oeci.eu/) | In English | → Research institutes → Oncology → Europe | 
| OEGGG | Österreichische Gesellschaft für Gynäkologie und Geburtshilfe (www.oeggg.at) | In German | → Gynaecology → Obstetrics → Austria | 
| OEKE | Organizaĵo por Ekonomiaj Kunlaboro kaj Evoluigo | In Esperanto | → Economics | 
| OEP | Observatoire Européen du Plurilinguisme | In French | → Language, linguistics, literature | 
| OESI | Oficina del Español en la Sociedad de la Información (http://oesi.cervantes.es) | In Spanish | → Linguistics → Computer science | 
| OFA | Orthopedic Foundation for Animals (www.offa.org) | In English | → Foundations → Veterinary medicine | 
| ÖFAI | Österreichisches Forschungsinstitut für Artificial Intelligence (www.ofai.at) | In German | → Research institutes → Artificial intelligence → Austria | 
| OFAJ | Office Franco-Allemand pour la Jeunesse | In French | → International relations | 
| OFB | Oost Flakkese Boys | In Dutch | → Sport, physical exercises | 
| OFC | Oostzaanse Football Club | In Dutch | → Football and rugby | 
| ÖFG | Österreichische Forschungsgemeinschaft (www.oefg.at) | In German | → Research institutes → Research policy → Austria | 
| OFI | Österreichisches Forschungsinstitut für Chemie und Technik (www.ofi.co.at) | In German | → Research institutes → Chemistry → Chemical technology → Austria | 
| OFM | Ordo Fratrum Minorum | In Latin | → Christianity | 
| ÖFSE | Österreichische Forschungsstiftung für Entwicklungshilfe (www.oefse.at) | In German | → Foundations → Development → Austria | 
| Ofta | Observatoire Français des Techniques Avancées | In French | → Research institutes → Engineering, technology | 
| ÖFV | Österreichisch-Französische Vereinigung (www.oefv.org) | In German | → International relations → Austria | 
| ÖFZ | Österreichisch-Französisches Zentrum für wirtschaftliche Annäherung in Europa | In German | → Economics → Austria | 
| ÖGA | Österreichische Gesellschaft für Außenpolitik und Internationale Beziehungen | In German | → International relations → Austria | 
| ÖGA | Österreichische Gesellschaft für Akupunktur (www.akupunktur.at) | In German | → Pharmacology, toxicology → Austria | 
| ÖGAA | Österreichische Gesellschaft für Astronomie und Astrophysik (www.oegaa.at) | In German | → Astronomy → Austria | 
| ÖGAI | Österreichische Gesellschaft für Allergologie und Immunologie (www.oegai.org) | In German | → Immunology and allergy → Austria | 
| ÖGAM | Österreichische Gesellschaft für Allgemeinmedizin (www.oegam.at) | In German | → Medicine → Austria | 
| ÖGAM | Österreichische Gesellschaft für Allgemein- und Familienmedizin = ELNA | Esperanto-Ligo de Nord-Ameriko | In Esperanto = ELNA | Esperanto League for North America | In English | In German | → Medicine → Austria | 
| ÖGARI | Österreichische Gesellschaft für Anaesthesiologie, Reanimation und Intensivmedizin (www.oegari.at) | In German | → Traumatology → Anesthesiology → Austria | 
| ÖGB | Österreichischer Gewerkschaftsbund (www.oegb.at) | In German | → Labour, labour economics → Austria | 
| OGBL | Onofhängege Gewerkschaftsbond Lëtzebuerg | In Letzeburgesh | → Labour, labour economics | 
| ÖGBM | Österreichische Gesellschaft für Biochemie und Molekularbiologie | In German | → Biochemistry, biophysics → Austria | 
| ÖGBT | Österreichische Gesellschaft für Biotechnologie (www.oegbt.org) | In German | → Biotechnology → Austria | 
| OGC | Open Geospatial Consortium | In English | → Computer science → Geodesy, cartography | 
| ÖGDV | Österreichische Gesellschaft für Dermatologie und Venerologie (www.oegdv.at) | In German | → Dermatology → Austria | 
| OGE | Ordre des Géomètres Experts | In French | → Geodesy, cartography | 
| ÖGfL | Österreichische Gesellschaft für Literatur (www.ogl.at) | In German | → Literature → Austria | 
| ÖGGG | Österreichische Gesellschaft für Geriatrie und Gerontologie (www.geriatrie-online.at) | In German | → Gerontology → Austria | 
| ÖGGGT | Österreichische Gesellschaft für Genetik und Gentechnologie (www.oegggt.org) | In German | → Genetics → Biotechnology → Austria | 
| ÖGGH | Österreichische Gesellschaft für Gastroenterologie und Hepatologie (www.oeggh.at) | In German | → Pathology → Austria | 
| OGHB | Office Généalogique et Héraldique de Belgique | In French | → Genealogy → Heraldry → Belgium | 
| ÖGHMP | Österreichische Gesellschaft für Hygiene, Mikrobiologie und Präventivmedizin (www.oeghmp.at) | In German | → Personal health and hygiene → Public health and hygiene → Microbiology → Austria | 
| ÖGHO | Österreichische Gesellschaft für Hämatologie und Onkologie (www.oegho.at) | In German | → Blood and circulatory system → Oncology → Austria | 
| ÖGI | Österreichisches Gießerei-Institut (www.ogi.at) | In German | → Research institutes → Metallurgy → Austria | 
| ÖGI | Österreichisches Getränke-Institut (www.oegi.at) | In German | → Research institutes → Beverage industry → Austria | 
| ÖGIG | Österreichische Gesellschaft für Informatikgeschichte (www.oegig.at) | In German | → History → Computer science → Austria | 
| ÖGIM | Österreichische Gesellschaft für Innere Medizin (www.oegim.at) | In German | → Medicine → Austria | 
| ÖGK | Österreichisches Grünes Kreuz (www.gruenes-kreuz.org) | In German | → Medicine → Austria | 
| OGKA | Österreichische Gesellschaft für kontrollierte Akupunktur (www.ogka.at) | In German | → Pharmacology, toxicology → Austria | 
| ÖGKC | Österreichische Gesellschaft für klinische Chemie | In German | → Biochemistry, biophysics → Pharmacology, toxicology → Austria | 
| ÖGKJ | Österreichische Gesellschaft für Kinder- und Jugendheilkunde (https://www.paediatrie.at/) | In German | → Pediatry → Austria | 
| ÖGLUT | Österreichische Gesellschaft für Lungenerkrankungen und Tuberkulose (www.oeglut.at) | In German | → Chest diseases → Infectious diseases → Austria | 
| ÖGN | Österreichische Gesellschaft für Neurologie (www.oegn.at) | In German | → Neurology → Austria | 
| ÖGN | Österreichische Gesellschaft für Nuklearmedizin (www.ogn.at) | In German | → Medicine → Austria | 
| ÖGP | Österreichische Gesellschaft für Pneumologie (www.ogp.at) | In German | → Chest diseases → Austria | 
| ÖGPB | Österreichische Gesellschaft für Neuropsychopharmakologie und Biologische Psychiatrie (www.oegpb.at) | In German | → Pharmacology, toxicology → Neurology → Psychiatry → Austria | 
| ÖGPH | Österreichische Gesellschaft für Public Health (www.oeph.at) | In German | → Public health and hygiene → Austria | 
| ÖGPMR | Österreichische Gesellschaft für Physikalische Medizin und Rehabilitation (www.oegpmr.at) | In German | → Medicine → Austria | 
| ÖGPPM | Österreichische Gesellschaft für Psychosomatische und Psychotherapeutische Medizin (www.psychotherapeutische-medizin.at) | In German | → Psychology → Austria | 
| ÖGRM | Österreichische Gesellschaft für Reproduktionsmedizin und Endokrinologie (www.oegrm.at) | In German | → Gynaecology → Austria | 
| ÖGRO | Österreichische Gesellschaft für Radioonkologie (www.oegro.com) | In German | → Oncology → Austria | 
| ÖGS | Österreichische Gesellschaft für Senologie (www.senologie.at) | In German | → Gerontology → Austria | 
| ÖGSMSF | Österreichische Gesellschaft für Schlafmedizin und Schlafforschung (www.schlafmedizin.at) | In German | → Medicine → Austria | 
| ÖGT | Österreichische Gesellschaft für Tuina (www.tuina.or.at) | In German | → Pharmacology, toxicology → Austria | 
| ÖGT | Österreichische Gesellschaft der Tierärzte (www.vu-wien.ac.at/oegt/) | In German | → Veterinary medicine → Austria | 
| ÖGUM | Österreichische Gesellschaft für Ultraschall in der Medizin (http://oegum.wiemat.at) | In German | → Medicine → Austria | 
| ÖGUT | Österreichische Gesellschaft für Umwelt und Technik (www.oegut.at) | In German | → Threats to the environment → Environmental technology, water supply, waste management → Austria | 
| ÖGV | Österreichischer Gewerbeverein (www.gewerbeverein.at) | In German | → Economics → Austria | 
| OHA | Oral History Association | In English | → Associations → History | 
| OHM | Organisatie voor Hindoe Media (www.ohmnet.nl) | In Dutch | → Netherlands | 
| OHT | Organization of History Teachers | In English | → Education → History | 
| OHVV | Ouden Hoornse Voetbal Vereniging | In Dutch | → Football and rugby → Netherlands | 
| OIAC | Organisation pour l'Interdiction des Armes Chimiques (www.opcw.org) = OPWC | Organisation for the Prohibition of Chemical Weapons | In English | In French | → International relations → Military engineering | 
| ÖIAT | Österreichisches Institut für angewandte Telekommunikation (www.oiat.at) | In German | → Research institutes → Telecommunications → Austria | 
| OIB | Österreichisches Institut für Bautechnik (www.oib.or.at) | In German | → Civil engineering → Construction → Austria | 
| OIBT | Organisation Internationale des Bois Tropicaux (www.itto.or.jp) = ITTO | International Tropical Timber Organization | In English = OIMT | Organización Internacional de las Maderas Tropicales | In Spanish | In French | → Environmental protection → Timber and woodworking industry | 
| OIC | Organization of the Islamic Conference | In English | → Islam → International relations | 
| OIC | Organisation of the Islamic Conference | In English | → Islam | 
| OICA | Oklahoma Institute for Child Advocacy | In English | → Social welfare → Education → United States | 
| OICA | Organisation Internationale des Constructeurs d'Automobiles (http://oica.net) | In French | → Mechanical engineering → Automobile manufacturing | 
| OIE | Office International des Épizooties (www.oie.int) | In French | → Veterinary medicine | 
| OIEau | Office International de l'Eau | In French | → Hydrology → Environmental technology, water supply, waste management | 
| OIETAI | Organization for Investment, Economic and Technical Assistance of Iran | In English | → Economics → 33972 | 
| OIF | Osteogenesis Imperfecta Foundation | In English | → Foundations → Pathology | 
| ÖIIP | Österreichisches Institut für Internationale Politik (www.oiip.at) | In German | → Research institutes → International relations → Austria | 
| ÖIJ | Österreichisches Institut für Jugendforschung (www.oeij.at) | In German | → Research institutes → Social sciences → Austria | 
| OIML | Organisation Internationale de Métrologie Légale | In French | → Standardization | 
| OIMT | Organización Internacional de las Maderas Tropicales (www.itto.or.jp) = OIBT, ITTO (look above) | In Spanish | → Environmental protection → Timber and woodworking industry | 
| ÖIN | Österreichisches Institut für Nachhaltige Entwicklung | In German | → Research institutes → Austria | 
| OING | Organización Internacional No Gubernamental | In Spanish | |
| OIPC | Organisation Internationale de Police Criminelle | In French | → International relations → Criminology → Police | 
| OIQ | Ordre des Ingénieurs du Québec (www.oiq.qc.ca) | In French | → Engineering, technology | 
| OIV | Organisation Internationale de la Vigne et du Vin | In French | → Agricultural sciences → Beverage industry | 
| OJC | Organisation Juive de Combat | In French | → Judaism → History | 
| OJC | ODI Juliana Combinatie | In Dutch | → Sport, physical exercises | 
| OKACOM | Okavango River Basin Water Commission | In English | → Hydrology → Environmental technology, water supply, waste management | 
| ÖKG | Österreichische Kardiologische Gesellschaft (www.atcardio.at) | In German | → Cardiology → Austria | 
| ÖKISTA | Österreichisches Komitee für Internationalen Studentenaustausch | In German | → International relations → Higher education, universities → Austria | 
| OKSV | Overlangel en Keentse Voetbal Club | In Dutch | → Football and rugby | 
| ÖKU | Österreichisches Komitee für Unfallverhütung im Kindesalter | In German | → Austria | 
| OKVC | Oldehoven Kommerzijlse Voetbal Club | In Dutch | → Football and rugby | 
| OL | Olympique Lyonnais (www.olweb.fr) | In French | → Sport, physical exercises → France | 
| OLIVEO | Onze Leus Is Vooruit En Overwinnen | In Dutch | → Sport, physical exercises | 
| OLIVIO | Onze Leus Is Voorwaarts In Overwinning | In Dutch | → Sport, physical exercises | 
| OMC | OSS Merwesteijn Combinatie | In Dutch | → Sport, physical exercises | 
| ÖMCCV | Österreichische Morbus Crohn-Colitis ulcerosa Vereinigung (www.oemccv.at) | In German | → Pathology → Austria | 
| OMG | Object Management Group | In English | → Software | 
| OML | Oddział Metali Lekkich | In Polish | → Research institutes → Metallurgy | 
| OMM | Organisation Météorologique Mondiale (www.wmo.int) = MMO | Monda Meteologia Organizo | In Esperanto = WMO | World Meteorological Organization | In English | In French | → Meteorology, climatology → United Nations | 
| OMNSH | Observatoire des Mondes Numériques en Sciences Humaines (www.omnsh.org) | In French | → Computer science → Social sciences | 
| OMSP | Organización Mundial de la Salud Pública | In Spanish | → International relations → Public health and hygiene | 
| OMVG | Organisation pour la Mise en Valeur du fleuve Gambie | In French | → Development → 5023 → Engineering, technology | 
| OMVS | Organisation pour la Mise en Valeur du fleuve Sénégal | In French | → 337 → Development → Agricultural sciences | 
| ON | Österreichisches Normungsinstitut (www.on-norm.at) | In German | → Standardization → Austria | 
| ONA | Ontspanning Na Arbeid | In Dutch | → Sport, physical exercises | 
| ONB | Op Nije Begon'n | In Dutch | → Sport, physical exercises | 
| ONDO | Op Naar De Overwinning | In Dutch | → Sport, physical exercises | 
| ONDRP | Observatoire National de la Délinquance et des Réponses Pénales | In French | → Police → Criminal law → 3438 | 
| ONE | Organisation Naturiste Européenne (www.onenaturism.com) | In English |