| NWN Ltd | Construction | 2006 |
| O J Joinery Limited | Construction | 2008 |
| Oak Rock Developments Ltd | Hospitality | 2026 |
| Oak Tree Farm Wedding Venue Ltd | Hospitality | 2024 |
| Oakenheart Tree Services LLP | | 2026 |
| Oakland Freehold Limited | Professional & scientific | 2017 |
| Objective Knowledge Limited | Professional & scientific | 1993 |
| Occhnet Limited | Health & social care | 1997 |
| Ocean Beach Grill Limited | Hospitality | 2022 |
| Oche UK Ltd | Hospitality | 2021 |
| Octopus (UK) Limited | Arts & recreation | 1998 |
| ODD JOB JON Limited | Other services | 2019 |
| Office Furniture Solutions Ltd | Wholesale & retail | 2013 |
| Ogmore Terrace Flats Management Company Ltd | Real estate | 1997 |
| OIL 4 Wales Limited | Wholesale & retail | 2010 |
| OIL and Renewable Energy 4 GB Limited | Extraterritorial | 2019 |
| OIL and Renewable Energy 4 Wales Limited | Extraterritorial | 2019 |
| OK Hub Ltd | Arts & recreation | 2026 |
| Old Bell 3 Ltd | Professional & scientific | 2005 |
| Old Oak Finance Company Limited | Financial services | 1938 |
| Ollizar Project Management Ltd | Construction | 2017 |
| ON Your Face Ltd | Arts & recreation | 2022 |
| One Ellie Ltd | Health & social care | 2022 |
| Online CAB Solutions Wales Limited | Transport & logistics | 2019 |
| Online Plastic Products Limited | Wholesale & retail | 2013 |
| Onwards N Upwards Ltd | Real estate | 2025 |
| Open Air Film & Chill Limited | Information & communication | 2017 |
| Opulence Obtain Ltd | Wholesale & retail | 2022 |
| Orange Juice Works Ltd | Manufacturing | 2021 |
| Oreknot Creative Hub Limited | Education | 2014 |
| Oren Construction Ltd | Construction | 1998 |
| Origin Dyfed Limited | Arts & recreation | 1991 |
| ORJ LHP CYF | Financial services | 2024 |
| Osborne Sureties Ltd | Administrative & support | 2025 |
| OSE Group (Holding) Ltd | Financial services | 2025 |
| OSE Group (Medical) Ltd | Health & social care | 2024 |
| OSS Developers Limited | Construction | 2024 |
| Oswald Davies (Electrical Supplies) Limited | Construction | 1953 |
| Overtoyou Ltd | Professional & scientific | 2023 |
| Owens Carpentry Ltd | Construction | 2025 |
| P & J Odley Limited | Wholesale & retail | 2011 |
| P and R Networks Ltd | Construction | 2017 |
| P H James Developments Ltd | Construction | 2022 |
| P L Wilson Limited | Agriculture & fishing | 2012 |
| P.D. Styles & Co Limited | Professional & scientific | 1999 |
| P.E. Dalton Limited | Construction | 2002 |
| Packpro UK Limited | Wholesale & retail | 2007 |
| Packwise Limited | Administrative & support | 2026 |
| PAF Access Ltd | Construction | 2020 |
| Pamela Jenkins Ltd | Professional & scientific | 2015 |
| Panco Properties Ltd | Real estate | 2016 |
| Pant Y Cendy Limited | Health & social care | 2004 |
| Paradise Management Consultancy Limited | Professional & scientific | 2010 |
| Parc Cynog Community Interest Company | Other services | 2011 |
| Parc Cynog Dairy Limited | Agriculture & fishing | 2014 |
| Parc Dewi Sant Wellbeing Gardens CIC | Agriculture & fishing | 2026 |
| Parch Digital Limited | Information & communication | 2025 |
| Parcyrabbot Farm Limited | Agriculture & fishing | 2011 |
| Parkend Furniture Limited | Wholesale & retail | 2021 |
| Parry and SON Builders (PSB) Ltd | Construction | 2023 |
| PARTS4GYMS Limited | Arts & recreation | 2019 |
| Passenger Transport Services Limited | Administrative & support | 2023 |
| Pasture Farming Limited | Agriculture & fishing | 2019 |
| Pasture Perfect Ltd | Hospitality | 2025 |
| Patrick Raymond Consultancy Ltd | Information & communication | 2023 |
| Paul Marke Films Ltd | Information & communication | 2018 |
| Paul the Sprayer Limited | Construction | 2026 |
| Pauldeen Limited | Professional & scientific | 2020 |
| Peak Line Engineering Ltd | Wholesale & retail | 2025 |
| Peak Line Properties Ltd | Real estate | 2026 |
| Peakline Motors Limited | Wholesale & retail | 2026 |
| Pearson Farming Limited | Agriculture & fishing | 2015 |
| Pegasus Insulation Services Ltd | Construction | 2023 |
| Pembrey Airport Limited | Transport & logistics | 2023 |
| Pembrokeshire Energy Limited | Energy | 2017 |
| Pembrokeshire Lamb Ltd | Wholesale & retail | 2019 |
| Pembrokeshire Recycling Company Limited | Water & waste | 2004 |
| Pembs.Net Limited | Administrative & support | 1999 |
| Pen-Awel Limited | Real estate | 2022 |
| Penally Pubs Ltd | Hospitality | 2024 |
| Penbryn Park Limited | Hospitality | 2023 |
| Penderyn Properties Limited | Real estate | 2015 |
| Pendine Community CIC | Hospitality | 2026 |
| Pendine Kayak Limited | Administrative & support | 2017 |
| Pendine Management Ltd | Hospitality | 2025 |
| Penffynnon Farm Ltd | Agriculture & fishing | 2023 |
| Pengwinau Bach Ltd | Health & social care | 2019 |
| Penhill Farm (Ferryside) Limited | Agriculture & fishing | 1957 |
| Peniel Community Association | Other services | 2008 |
| Penlan Argoed Limited | Agriculture & fishing | 2002 |
| Penllynin Enterprises Limited | Financial services | 2024 |
| Pentremeurig Farm Limited | Agriculture & fishing | 2007 |
| Penycoed Dairy Ltd | Agriculture & fishing | 2019 |
| Penycoed Farms Leisure Ltd | Hospitality | 2006 |
| Perinatal MH Training CIC | Health & social care | 2020 |
| Peripaton Limited | Health & social care | 2025 |
| Perrybone & Co Ltd | Hospitality | 2020 |
| Peter Francis Auctioneers Ltd | Other services | 2008 |
| Peter Weldon Iron Designs Ltd | Manufacturing | 2006 |
| Peterwell Estates Ltd | Hospitality | 2018 |