| ONUKA | Onuka | Onuka (альбом) |
| Onuphrius | Onur Air | Onychodactylus |
| Onychodactylus fischeri | Onychodontidae | Onychodontiformes |
| Onychogalea | Onychogalea fraenata | Onychogalea lunata |
| Onychogalea unguifera | Onychophora | Onychoprion fuscatus |
| Onychopterocheilus pallasii | Onychopteryx | Onychopteryx simpsoni |
| Onymacris unguicularis | Onyx (гурт) | Oсобняк Кріндача |
| Oodji | OOEP | Ooh La La |
| Oohkotokia | Oohkotokia horneri | Oomph |
| Oomph! | Oomycetes | Oomycota |
| OOo | Oophaga | Oophaga pumilio |
| Oops! I Did It Again: The Best of Britney Spears | Oops!.. I Did It Again | Oops!... I Did It Again |
| Oops!... I Did It Again - The Best Of Britney Spears | Oops!... I Did It Again - The Best of Britney Spears | OOPSLA |
| OOSP2 | OoVoo | OOXML |
| Op-ed | Opa (programming language) | Opa (мова програмування) |
| OPA1 | OPA3 | Opabinia |
| OPAC | OPAL (газогін) | OPALIN |
| OPC | OPCML | OPCW |
| Opeatogenys | Opeatogenys cadenati | Opeatogenys gracilis |
| Opel | Opel 4/8 PS | Opel Adam |
| Opel Admiral | Opel Agila | Opel Ampera |
| Opel Antara | Opel Arena | Opel Ascona |
| Opel Astra | Opel Astra F | Opel Astra G |
| Opel Astra H | Opel Astra J | Opel Astra K |
| Opel Astra OPC | Opel Astra OPS | Opel Calibra |
| Opel Campo | Opel Cascada | Opel Combo |
| Opel Commodore | Opel Corsa | Opel Corsa D |
| Opel Crossland X | Opel Diplomat | Opel Frontera |
| Opel Grandland X | Opel GT | Opel GT (Roadster) |
| Opel Insignia | Opel Kadet | Opel Kadett |
| Opel Kadett D | Opel Kadett E | Opel Kapitan |
| Opel Kapitän | Opel Karl | Opel Manta |
| Opel Meriva | Opel Mokka | Opel Monterey |
| Opel Monza | Opel Movano | Opel Olympia |
| Opel Omega | Opel Rekord | Opel Senator |
| Opel Signum | Opel Sintra | Opel Speedster |
| Opel Tigra | Opel Vectra | Opel Vivaro |
| Opel Zafira | Opel-Multec | Open 60 |
| Open air | Open AJAX | Open Babel |
| Open BSD | Open Budget | Open Build Service |
| Open Clip Art Library | Open Computing Language | Open Content Alliance |
| Open Database Connectivity | Open Database License | Open Design Alliance |
| Open Directory Project | Open Document Format | Open Document Text |
| Open Doors | Open Educational Resources | Open Encyclopedia Project |
| Open Enterprise Server | Open Gaz de France | Open Gaz de France 1993, одиночний розряд |
| Open Gaz de France 1994, одиночний розряд | Open Gaz de France 1995, одиночний розряд | Open Gaz de France 1996, одиночний розряд |
| Open Gaz de France 1997, одиночний розряд | Open Gaz de France 1998, одиночний розряд | Open Gaz de France 1999, одиночний розряд |
| Open Gaz de France 2000, одиночний розряд | Open Gaz de France 2001, одиночний розряд | Open Gaz de France 2002, одиночний розряд |
| Open Gaz de France 2003, одиночний розряд | Open Gaz de France 2004, одиночний розряд | Open Gaz de France 2005, одиночний розряд |
| Open Gaz de France 2006, одиночний розряд | Open Gaz de France 2007, одиночний розряд | Open Gaz de France 2008, одиночний розряд |
| Open GDF Suez | Open GDF Suez 2009, одиночний розряд | Open GDF Suez 2010, одиночний розряд |
| Open GDF Suez 2011, одиночний розряд | Open GDF Suez 2012, одиночний розряд | Open GDF Suez 2013, одиночний розряд |
| Open GDF Suez 2014, одиночний розряд | Open Geospatial Consortium | Open Handset Alliance |
| Open Happiness | Open ICEcat | Open Invention Network |
| Open Kids | Open Library | Open Mobile Alliance |
| Open Shortest Path First | Open Software License | Open Solaris |
| Open Sound Control | Open Source | Open source |
| Open Source Development Labs | Open Source Initiative | Open Systems Interconnection |
| Open Systems Interconnection Reference Model | Open Ukraine | Open Virtualization Format |
| Open vSwitch | Open webOS | Open Whisper Systems |
| Open XML Paper Specification | Open Your Eyes | Open Your Eyes (альбом Goldfinger) |
| Open Your Eyes (пісня Guano Apes) | Open-source | Open64 |
| OpenACC | OpenAI | OpenAL |
| OpenAPI | OpenAPI Specification | OpenArena |
| Openbox | Openbravo | Openbravo POS |
| OpenBSD | OpenBTS | OpenCart |
| Opencart | OpenCL | Opencms |
| OpenCms | OpenConnect | Openconnect |
| OpenCV | OpenCyc | Opendatabot |
| OpenDevelop GNU/Linux | OpenDisc | OpenDNS |
| OpenDocument | OpenDocument Format | OpenDWG |
| OpenEXR | OpenFeint | OpenFOAM |
| OpenFST | Opengamer | OPENGAMER |
| Opengamer.com.ua | OpenGL | OpenGL ES |
| OpenGL Shading Language | OpenHMPP | OpenID |
| OpenIndiana | OpenJDK | OpenLiteSpeed |
| OpenMAX | OpenMeetings | Openmeetings |
| OpenMP | OpenNebula | OpenNET |
| Opennet.ru | OpenOffice | OpenOffice Base |
| OpenOffice Calc | OpenOffice Draw | OpenOffice Impress |
| OpenOffice Math | OpenOffice Writer | OpenOffice XML |
| Openoffice.org | OpenOffice.org | OpenOffice.org Base |
| OpenOffice.org Calc | OpenOffice.org Draw | OpenOffice.org Impress |
| OpenOffice.org Math | OpenOffice.org Writer | OpenOrienteering Mapper |
| OpenPAM | OpenProcurement | OpenProj |
| OpenProject | OpenROV | OpenSceneGraph |
| OpenSeaMap | OpenSearch | OpenSER |
| OpenShot | OpenSL ES | OpenSolaris |
| Opensolaris | OpenSPARC | OpenSSH |
| OpenSSL | Openssl | OpenStack |
| Openstat | OpenStat | OpenStreetMap |
| Openstreetmap | OpenSUSE | Opentype |
| OpenType | OpenTyrian | OpenURL |
| OpenVAS | OpenVG | OpenVMS |
| OpenVMS кластери | OpenVPN | OpenVX |
| OpenVZ | OpenWindows | OpenWrt |
| OpenWRT | Opera | Opera (web browser) |
| Opera (браузер) | Opera Dragonfly | Opera Mail |
| Opera mail | Opera Max | Opera mini |
| Opera Mini | Opera Mobile | Opera Mobile Store |
