| Orchestra of ST. John's Limited | Arts & recreation | 1983 |
| Original Ginger Material Limited | Arts & recreation | 2018 |
| Orion Farming Group Limited | Other services | 2001 |
| Orion-Line Limited | Transport & logistics | 2018 |
| Oritz Consultancy Ltd. | Information & communication | 2013 |
| ORM Fencing Limited | Construction | 2024 |
| Orpam Ltd | Wholesale & retail | 2025 |
| Ortho Hemel Limited | Health & social care | 2015 |
| Orthoeurope Limited | Manufacturing | 1989 |
| Orthomobility Ltd | Manufacturing | 2004 |
| Orthoplus LLP | | 2009 |
| Orthoplussmiles Limited | Health & social care | 2020 |
| Orthox Holdings Limited | Professional & scientific | 2014 |
| Orundas Ltd | Transport & logistics | 2020 |
| Osiris Oxfordshire Limited | Information & communication | 2023 |
| Osmond Lange UK Ltd | Professional & scientific | 2023 |
| Osprey IT Consultancy Ltd | Information & communication | 2007 |
| Osse Asset Lending Limited | Other services | 2023 |
| Osse Forestry Limited | Agriculture & fishing | 2022 |
| Osse Publishing Limited | Information & communication | 2025 |
| Otel Bukleti SAN. TIC. Ltd | Wholesale & retail | 2025 |
| OUT of Balance Limited | Professional & scientific | 2023 |
| OUT of Bounds Limited | Arts & recreation | 2025 |
| Ovation Design Ltd | Construction | 2025 |
| Owen Developments Limited | Manufacturing | 2003 |
| Owsnett International Limited | Construction | 2016 |
| OX Pasture Property Limited | Agriculture & fishing | 2003 |
| OX Removals Ltd | Transport & logistics | 2024 |
| OX14 Ltd | Financial services | 2019 |
| Oxai Development Ltd | Real estate | 2016 |
| Oxber IT LLP | | 2025 |
| Oxbridge Editorial Services Ltd | Other services | 2025 |
| Oxbuilder Ltd | Construction | 2019 |
| Oxcion Limited | Professional & scientific | 2009 |
| Oxcode Consultancy Ltd | Information & communication | 2025 |
| Oxehealth Limited | Information & communication | 2012 |
| Oxford AI Centre Ltd | Education | 2025 |
| Oxford Air Conditioning Limited | Construction | 2006 |
| Oxford Algorithms Ltd | Information & communication | 2020 |
| Oxford BEE OPS Ltd | Professional & scientific | 2023 |
| Oxford Bike Works Ltd | Manufacturing | 2013 |
| Oxford Biosystems Limited | Wholesale & retail | 2001 |
| Oxford Blue Softwash Ltd | Extraterritorial | 2018 |
| Oxford Broadcast Consultants Limited | Professional & scientific | 2014 |
| Oxford Commercial Kitchens Limited | Manufacturing | 2006 |
| Oxford Drive Solutions Limited | Transport & logistics | 2022 |
| Oxford Drylining Ltd | Construction | 2016 |
| Oxford Eco Cars Ltd | Transport & logistics | 2024 |
| Oxford Edits Ltd | Professional & scientific | 2023 |
| Oxford Education Advice Limited | Professional & scientific | 2009 |
| Oxford Engineering Limited | Manufacturing | 1967 |
| Oxford Exclusif Tutorial Agency Limited | Education | 2008 |
| Oxford Flash Fiction Prize CIC | Information & communication | 2021 |
| Oxford Franchise Solutions Limited | Professional & scientific | 2019 |
| Oxford Freight Group Limited | Transport & logistics | 2010 |
| Oxford Fusion Technologies Ltd | Professional & scientific | 2020 |
| Oxford Gate Properties Limited | Real estate | 2020 |
| Oxford Golf Club Shop Ltd | Wholesale & retail | 2015 |
| Oxford Grab Hire Ltd | Water & waste | 2023 |
| Oxford Grazing Co Ltd | Wholesale & retail | 2023 |
| Oxford Growth Services Ltd | Professional & scientific | 2015 |
| Oxford Heating Supplies Limited | Wholesale & retail | 2016 |
| Oxford Hideaways Ltd | Construction | 2026 |
| Oxford Immunotec Global Limited | Manufacturing | 2013 |
| Oxford Immunotec Limited | Manufacturing | 2002 |
| Oxford Karate Academy Ltd | Education | 2020 |
| Oxford Kitchen Culture Ltd | Wholesale & retail | 2018 |
| Oxford Leadership Ltd | Professional & scientific | 2026 |
| Oxford Logistic Limited | Transport & logistics | 2022 |
| Oxford Marble Specialist Ltd | Manufacturing | 2023 |
| Oxford Maritime Limited | Administrative & support | 1998 |
| Oxford Maritime Research Limited | Manufacturing | 2020 |
| Oxford Marketing Associates Limited | Professional & scientific | 2009 |
| Oxford Mobile X-Ray Ltd | Professional & scientific | 2022 |
| Oxford Mortgage Services Limited | Financial services | 2005 |
| Oxford Nanoscience Limited | Manufacturing | 2025 |
| Oxford Natural Products Limited | Extraterritorial | 2020 |
| Oxford Oak Installations Ltd | Construction | 2018 |
| Oxford Open Learning Trust Ltd | Education | 2006 |
| Oxford Performance Coaching Ltd | Education | 2026 |
| Oxford Pharmagenesis Holdings Limited | Information & communication | 2012 |
| Oxford Pipework Services Limited | Construction | 1998 |
| Oxford Plant Hire Ltd | Administrative & support | 2019 |
| Oxford Property Solutions Ltd | Construction | 2025 |
| Oxford Sales Consulting Associates Limited | Professional & scientific | 2023 |
| Oxford Surveyors Limited | Professional & scientific | 2010 |
| Oxford Transport Ltd | Transport & logistics | 2021 |
| Oxford White Horse Property Management Limited | Real estate | 2023 |
| Oxford Wood Recycling Ltd | Water & waste | 2005 |
| Oxford Young Steps | Health & social care | 2007 |
| Oxfordshire Building & Stoves Limited | Construction | 2017 |
| Oxfordshire Concrete Limited | Manufacturing | 2018 |
| Oxfordshire Dental Hygiene Limited | Health & social care | 2020 |
| Oxfordshire Football Development Ltd | Arts & recreation | 2015 |
| Oxfordshire Heating and Property Services Limited | Construction | 2017 |
| Oxfordshire Logistics Ltd | Transport & logistics | 2016 |
| Oxfordshire Mobile Bar Hire Ltd | Hospitality | 2025 |
| Oxfordshire Towbars Ltd | Wholesale & retail | 2025 |
| Oxgate Trading Ltd | Wholesale & retail | 2026 |
| Oxlec Ltd | Construction | 2023 |