| O Newcombe Plastering and Renovations Ltd | Real estate | 2024 |
| O R C P Limited | Wholesale & retail | 2016 |
| O Ribatejo Bar Ltd | Hospitality | 2024 |
| O Ribatejo Leicester Ltd | Hospitality | 2024 |
| O&A Tech Ltd | Information & communication | 2011 |
| O&M Fashion Limited | Wholesale & retail | 2024 |
| O&T Limited | Real estate | 2020 |
| O'Connor Real Estate Limited | Real estate | 2021 |
| O'Connor Wealth Management Limited | Financial services | 2005 |
| O'Hara Civil's Limited | Construction | 2013 |
| O'Keeffe Quality Consulting Limited | Professional & scientific | 2018 |
| O'Rourke (Midlands) Ltd | Construction | 2012 |
| O'Rourke Ducting Services Ltd | Construction | 2025 |
| O'Shea Property Ltd | Real estate | 2020 |
| O'Sheehan Properties Limited | Real estate | 2024 |
| O'Sullivan Property Holdings Limited | Real estate | 2016 |
| O.D. Engineering Ltd | Manufacturing | 2008 |
| O.L.D. Engineering Company Limited | Manufacturing | 1971 |
| O.N Global Investments Ltd | Real estate | 2023 |
| O.P Anwar Limited | Health & social care | 2014 |
| O1 Best Motors Ltd | Wholesale & retail | 2024 |
| O3 Catering Ltd | Hospitality | 2025 |
| O3 Facilities Management Ltd | Administrative & support | 2024 |
| O3 Training Limited | Education | 2025 |
| O4U Ltd | Construction | 2019 |
| OA Karim Limited | Real estate | 2025 |
| OA Optics Limited | Health & social care | 2017 |
| Oadby & Leicester Gymnastics Club Ltd | Arts & recreation | 2016 |
| Oadby & Wigston Borough Veteran Support ( Leicestershire ) Ltd | Other services | 2025 |
| Oadby 47 Limited | Households | 2021 |
| Oadby Aesthetics Ltd | Other services | 2024 |
| Oadby and Leicester Gymnastics Club (Midlands) Ltd | Arts & recreation | 2022 |
| Oadby Assignments Ltd | Transport & logistics | 2015 |
| Oadby Builders Leicester Ltd | Construction | 2022 |
| Oadby Builders Limited | Construction | 2023 |
| Oadby Building Plastics Limited | Wholesale & retail | 2007 |
| Oadby Community Hub CIC | Other services | 2025 |
| Oadby DIY Limited | Wholesale & retail | 1999 |
| Oadby Estate Agents Limited | Real estate | 2008 |
| Oadby Estates Limited | Real estate | 2006 |
| Oadby Golf Club Ltd | Extraterritorial | 2012 |
| Oadby Healthcare Ltd | Health & social care | 2025 |
| Oadby Holdings Limited | Financial services | 2023 |
| Oadby House Limited | Wholesale & retail | 2024 |
| Oadby Kitchen & Catering Ltd | Hospitality | 2023 |
| Oadby Kitchen Limited | Hospitality | 2023 |
| Oadby Laundry Ltd | Administrative & support | 2025 |
| Oadby Meat & Grocers Ltd | Wholesale & retail | 2024 |
| Oadby Oriental Chef Limited | Hospitality | 2026 |
| Oadby Parties & Tots Limited | Other services | 2022 |
| Oadby PC Repairs Ltd | Manufacturing | 2018 |
| Oadby Plastics Group Limited | Extraterritorial | 2022 |
| Oadby Plastics Holdings Limited | Manufacturing | 2017 |
| Oadby Plastics Limited | Manufacturing | 1998 |
| Oadby POP UP Bars Ltd | Hospitality | 2019 |
| Oadby Posts Limited | Transport & logistics | 2026 |
| Oadby Property Services Ltd | Real estate | 2009 |
| Oadby Renovations Limited | Construction | 2023 |
| Oadby Self Storage Ltd | Transport & logistics | 2023 |
| Oadby Sushi Limited | Hospitality | 2021 |
| Oadby Taxis Ltd | Transport & logistics | 2023 |
| Oadby Town Football Club Ltd | Arts & recreation | 2024 |
| Oadby Van Centre Ltd | Wholesale & retail | 2022 |
| Oadby Vapes Ltd | Wholesale & retail | 2018 |
| Oadby Wyggestonian Rugby Football Club Limited | Arts & recreation | 2009 |
| Oadby, Wigston and Leicestershire Schools Academy Trust | Education | 2013 |
| OAG Printers Limited | Manufacturing | 2025 |
| OAI Consulting Limited | Administrative & support | 2018 |
| Oak Automatics Limited | Arts & recreation | 2002 |
| Oak Construction Projects Limited | Construction | 2023 |
| Oak House Kitchen Consultancy Limited | Education | 2019 |
| Oak House Kitchen Limited | Information & communication | 2019 |
| Oak Knoll Property Ltd | Real estate | 2025 |
| Oak Smart Technology Limited | Information & communication | 2017 |
| Oak Spinney Holdings Limited | Financial services | 2016 |
| Oak Stone Apartments Ltd | Real estate | 2018 |
| Oak Stone Works Ltd | Real estate | 2015 |
| Oak Tree Operations Limited | Professional & scientific | 2024 |
| Oak Tree Property Developments Ltd | Real estate | 2022 |
| Oak Valley Security Systems Limited | Administrative & support | 2018 |
| Oakdale (Leicester) Limited | Real estate | 1999 |
| Oakdale Care Limited | Health & social care | 2022 |
| Oakenshaw Skills Ltd | Wholesale & retail | 2015 |
| Oakfield Park Properties Limited | Real estate | 2023 |
| Oakham Supermarket Ltd | Wholesale & retail | 2022 |
| Oakhill Publishing Limited | Information & communication | 2005 |
| Oakland Interiors Ltd | Construction | 2017 |
| Oakland Press Tool Company Limited | Extraterritorial | 1960 |
| Oaklands Sun Club Limited | Arts & recreation | 2025 |
| Oakleaf Contracting Limited | Construction | 2003 |
| Oaklee Trading Limited | Construction | 2015 |
| Oakleigh Logistics Ltd | Transport & logistics | 2014 |
| Oakleigh Practice Limited | Health & social care | 2011 |
| Oakley (Leicester) Ltd | Other services | 2013 |
| Oakley Care Services Ltd | Health & social care | 2018 |
| Oakley Crafted Construction Limited | Construction | 2019 |
| Oakley Design & Build Ltd | Construction | 2022 |
| Oakley Joinery Limited | Construction | 2000 |
| Oakley Window Cleaning Limited | Administrative & support | 2022 |
| Oakline Property Holdings Ltd | Real estate | 2025 |