| Orca Airways | OrCAD | Orcaella |
| Orcaella brevirostris | Orcaella heinsohni | Orchestral Favorites |
| Orchestral Manoeuvres in the Dark | Orchid | Orchidaceae |
| Orchidoideae | Orchis | Orchis coriophora |
| Orchis elegans | Orchis mascula | Orchis militaris |
| Orchis morio | Orchis odoratissima | Orchis palustris |
| Orchis purpurea | Orchis simia | Orchis ustulata |
| ORCID | Orcinus | Orcinus orca |
| Orcs Must Die! Unchained | Orcus Patera | Ord |
| Order by | ORDER BY | Order by (SQL) |
| Order of the British Empire | Ordina Open | Ordina Open 2004, жінки, одиночний розряд |
| Ordina Open 2005, жінки, одиночний розряд | Ordina Open 2006, жінки, одиночний розряд | Ordina Open 2007, жінки, одиночний розряд |
| Ordina Open 2008, жінки, одиночний розряд | Ordina Open 2009, жінки, одиночний розряд | Ordnance QF 20 pounder |
| Ore no Imouto ga Konna ni Kawaii Wake ga Nai | Oreailurus jacobita | Oreamnos |
| Oreamnos americanus | Orectolobiformes | Orectolobus |
| Orectolobus floridus | Orectolobus halei | Orectolobus hutchinsi |
| Orectolobus japonicus | Orectolobus leptolineatus | Orectolobus maculatus |
| Orectolobus ornatus | Orectolobus parvimaculatus | Orectolobus reticulatus |
| Orectolobus wardi | Oregon State University | Oreina plagiata |
| Oreina viridis | Oreo | Oreochromis |
| Oreochromis mossambicus | Oreochromis niloticus | Oreoglanis |
| Oreopithecus | Oreopithecus bambolii | ORF |
| ORF (телеканал, Австрія) | Org mode | Org-mode |
| Org-Mode | Organ Thieves | Organic (альбом Джо Кокера) |
| Organic Land Grid Array | Organic light-emitting diode | Organic Soul |
| Organic Syntheses | ORGANIC UA | Organisation for Economic Co-operation and Development |
| Organisation for Economic Cooperation and Development | Organisation Internationale des Constructeurs d'Automobiles | Orgasmatron |
| Orgueil | Orgy in Rhythm | Ori and the Blind Forest |
| Oriana Music | Oribatida | Oricon |
| Oricon Charts | Orient | Orient Watch |
| Orient Watch Company | Orientales Omnes Ecclesias | Orientales, la Patria o la tumba |
| Orientalium Ecclesiarum | OrientDB | Orienteering |
| Orientus | Oriflame | Origanum |
| Origanum amanum | Origanum dictamnus | Origanum laevigatum |
| Origanum libanoticum | Origanum majorana | Origanum onites |
| Origanum rotundifolium | Origanum syriacum | Origanum vulgare |
| Origin | Origin (альбом) | Origin (платформа цифрової дистрибуції) |
| Origin of Symmetry | Origin of the Species | Origin: Spirits of the Past |
| Original equipment manufacturer | Original Film | Original Masters |
| Original Prankster | Original Single Kollektion | Original Single Kollektion (компіляція Rammstein) |
| Original Single Kollektionu (Rammstein) | Original Soundtrack | Original Soundtracks 1 |
| Original Video Animation | OriginGPS | Origo |
| Origo regis | Origo regis Jagyelo et Wytholdi ducum Lithuanie | Orillero |
| Orinocodoras | Orinocodoras eigenmanni | Oriola KD |
| Oriolidae | Oriolus | Oriolus bouroensis |
| Oriolus brachyrhynchus | Oriolus chlorocephalus | Oriolus crassirostris |
| Oriolus forsteni | Oriolus larvatus | Oriolus monacha |
| Oriolus nigripennis | Oriolus oriolus | Oriolus percivali |
| Oriolus phaeochromus | Oriolus sagittatus | Orion |
| Orion (судно) | Orion Cinema Network | Orion Pictures |
| Orionides | Orix | Orizont/La hotar |
| Orkut | Orlen | Orlitia |
| Orlitia borneensis | Orlyval | ORM |
| ORM1 | ORM2 | ORMDL1 |
| ORMDL2 | ORMDL3 | Ornimegalonyx |
| Ornithischia | Ornithocheiroidea | Ornithodira |
| Ornithogallum umbellatum | Ornithogalum | Ornithogalum adseptentrionesvergentulum |
| Ornithogalum amphibolum | Ornithogalum arabicum | Ornithogalum boucheanum |
| Ornithogalum narbonense | Ornithogalum oreoides | Ornithogalum orthophyllum |
| Ornithogalum refractum | Ornithogalum umbellatum | Ornithomimosauria |
| Ornithopoda | Ornithoptera alexandrae | Ornithopus compressus |
| Ornithopus pinnatus | Ornithorhychus | Ornithorhynchidae |
| Ornithorhynchus | Ornithorhynchus anatinus | Ornithoscelida |
| Ornithosuchidae | Ornithothoraces | Ornithurae |
| Ornithuromorpha | Orobanchaceae | Orobanche |
| Orobanche amethystea | Orobanche crenata | Orobanche minor |
| Orobanche ramosa | Orobanche sanguinea | Orobica |
| OROCHI | Orodontida | Oroxylum indicum |
| ORP Kujawiak (L72) | ORP Orkan (G90) | ORP Orzeł (1938) |
| ORP Orzeł (292) | ORP Piorun (G65) | ORP Sokół (1964) |
| Orphaned Land | Orrorin tugenensis | Ortega |
| Orthacanthus | Orthetrum sabina | Orthilia secunda |
| Orthochromis | Orthodera novaezealandiae | Orthogeomys |
| Orthogonal frequency division multiplexing | Orthogonal frequency-division multiple access | Orthohepadnavirus |
| Ortholixus | Orthomys | Orthomyxoviridae |
| Orthonectida | Orthopsittaca manilata | Orthoptera |
| Orthosiini | Orthotaenia obsoletana | Orthriophis |
| Orthrozanclus reburrus | Orussus abietinus | Orval |
| Oryctes | Oryctes nasicornis | Oryctes rhinoceros |
| Oryctolagus | Oryctolagus cuniculus | Oryx |
| Oryx beisa | Oryx dammah | Oryx gazella |
| Oryx leucoryx | Oryza | Oryza glaberrima |
| Oryza sativa | Oryzias | Oryzias latipes |
| Oryzias sinensis | Oryzomyini | Oryzomys |
| Oryzomys antillarum | Oryzomys couesi | Oryzomys curasoae |
| Oryzorictinae | Os | OS |
| Ӛ | Ҋ | Қ |
| Պ | OS (значення) | Ӛ (кирилиця) |
| Қ (кирилиця) | OS / 2 | OS Android |
| Os etmoidale | Os frontale | Os hyoideum |
| Os ilii | Os ischii | Os Mutantes |
| Os occipitale | Os palatinum | Os parietale |
| Os sphenoidale | Os temporales | OS X |
| OS X 10.9 | OS X El Capitan | OS X Mavericks |
| OS X Mountain Lion | OS X Server | OS X Sierra |
| OS X Yosemite | Os.wikipedia.org | OS/2 |
| OS/2 v1.0 | OS/2 v1.10EE | OS/2 v1.10SE |
| OS/2 v1.20 | OS/2 v1.30 | OS/2 v2.00 |
| OS/2 v2.10 | OS/360 | OS/370 |
| OS/VS | OS9 | Osagyefo Barge |
