| MR Wong Fish Bar and Chinee Takeaway Limited | Hospitality | 2026 |
| MRE Building Developments Ltd | Construction | 2021 |
| MT Polo Limited | Financial services | 2004 |
| Muglamania Limited | Wholesale & retail | 2005 |
| Multi-Span(Cardiff) Limited | Hospitality | 1970 |
| Murison's Holdings Ltd | Financial services | 2023 |
| Musselwick Trading Co. Ltd | Agriculture & fishing | 2011 |
| MW Surveys Ltd | Professional & scientific | 2025 |
| My Black Box Ltd | Education | 2025 |
| My Brand Boost Ltd | Administrative & support | 2025 |
| My Media CYF | Extraterritorial | 2024 |
| My Superhost Limited | Hospitality | 2022 |
| Myprescription Limited | Extraterritorial | 2004 |
| Myriddin Clearing International Ltd | Administrative & support | 2017 |
| Myscript IP Limited | Professional & scientific | 2017 |
| Myscript Limited | Wholesale & retail | 2004 |
| MÔR Aesthetics Limited | Other services | 2026 |
| N & D Watts Limited | Health & social care | 2023 |
| N.J. Mills Limited | Professional & scientific | 2017 |
| Nadis Ltd | Education | 2002 |
| Nardave Ltd | Other services | 2021 |
| National Alliance for School Attendance Ltd | Professional & scientific | 2016 |
| National Association for School Attendance Ltd | Other services | 2025 |
| Nature Power International Ltd | Administrative & support | 2020 |
| Natures Tropical Emporium Limited | Wholesale & retail | 2020 |
| Naughty Networks LP | | 2023 |
| Navar Falke Ltd. | Extraterritorial | 2025 |
| Naxim Ltd | Administrative & support | 2022 |
| NBD Developments Limited | Real estate | 1997 |
| NDD Service International Ltd | Administrative & support | 2025 |
| NE Rental Limited | Real estate | 2010 |
| Neil Harries Electrical Services Limited | Manufacturing | 2002 |
| Neuroflourish Training Limited | Education | 2025 |
| New Brothers House (Haverfordwest) Limited | Hospitality | 2024 |
| New Haven Estates Ltd | Real estate | 2026 |
| New Horizons 25 Ltd | Extraterritorial | 2025 |
| New Lifestyle Spirit Ltd | Extraterritorial | 2023 |
| New Stats LP | | 2022 |
| Newlay Contracting Limited | Manufacturing | 2015 |
| Nexa-Logic International Ltd | Administrative & support | 2025 |
| Nextlevel Impuls Ltd | Extraterritorial | 2025 |
| Nexus Imports Ltd | Wholesale & retail | 2024 |
| Neycare Limited | Other services | 2003 |
| Nial Rees (Services) Ltd | Professional & scientific | 2015 |
| Niche Cottages Limited | Extraterritorial | 2005 |
| Nicholas Jackson Associates Ltd | Professional & scientific | 2020 |
| Nigel Sinnett Consulting Limited | Professional & scientific | 2020 |
| Nigel YEA Agri Services Limited | Other services | 2012 |
| Nikelz Properties Ltd | Real estate | 2020 |
| Niloco Project LLP | | 2019 |
| Nishkara Ltd | Extraterritorial | 2022 |
| Nisoted Ltd | Other services | 2018 |
| Niwin Ltd | Other services | 2018 |
| Niwl Guitars Ltd | Manufacturing | 2025 |
| NK Urban Retail Ltd | Wholesale & retail | 2025 |
| Nolton Haven Holiday Cottages Limited | Hospitality | 2012 |
| Nolton Haven Quality Cottages Limited | Hospitality | 2014 |
| Nongba Invest Ltd | Financial services | 2023 |
| North Nash Farms Limited | Agriculture & fishing | 2002 |
| Nota Terra Ltd | Extraterritorial | 2024 |
| Nought Design Limited | Arts & recreation | 2015 |
| Nourish Pembrokeshire Ltd | Hospitality | 2022 |
| Novus International Ltd | Administrative & support | 2025 |
| Nrcmservices Ltd | Professional & scientific | 2025 |
| NSP Management Solutions Ltd | Construction | 2024 |
| Nuci Contracting Ltd | Other services | 2024 |
| Nutrasteward Limited | Professional & scientific | 2016 |
| Nutting Limited | Other services | 2017 |
| Nyshi Interior Services Ltd | Construction | 2012 |
| O & D Enterprises Limited | Hospitality | 1980 |
| O & N Living Ltd | Real estate | 2021 |
| O & N Properties Limited | Construction | 2013 |
| O G Fair Ltd | Health & social care | 2025 |
| O.C. Electrical Services Ltd | Construction | 2008 |
| Oak Tree Farm Limited | Agriculture & fishing | 1954 |
| Oakdale Homes (Pembrokeshire) Limited | Construction | 1992 |
| Oaklea Manor Limited | Hospitality | 1995 |
| Ocean Hair (Saundersfoot) Limited | Other services | 2003 |
| Ocean View Farm Ltd | Real estate | 2024 |
| Oceanview Solutions Ltd | Administrative & support | 2024 |
| Ocky White Travel Limited | Administrative & support | 2013 |
| OFA Trade Ltd | Wholesale & retail | 2024 |
| OFF the Hook Ltd | Hospitality | 2021 |
| Office Service DG Ltd | Administrative & support | 2025 |
| Old Farmhouse Brewery Ltd. | Manufacturing | 2019 |
| Oldhdam Ltd | Other services | 2018 |
| Olomoc Ltd | Administrative & support | 2022 |
| Olwen Holdings Ltd | Financial services | 2025 |
| Omnes Aditus Ltd | Manufacturing | 2017 |
| One Music Limited | Wholesale & retail | 2013 |
| One Music Publishing Limited | Information & communication | 2016 |
| One Stop Johnston Food Ltd | Hospitality | 2024 |
| One Stop Property Development Limited | Construction | 2011 |
| One Stop Window Shop (Pembrokeshire) Limited | Administrative & support | 2005 |
| One Way HOW Ltd | Professional & scientific | 2024 |
| Onestopsocial Ltd | Professional & scientific | 2014 |
| Online Entry System Limited | Arts & recreation | 2013 |
| OPTILIFE360 Ltd | Administrative & support | 2023 |
| Opulent Orchid Ltd | Wholesale & retail | 2025 |
| Orchard Start UP Limited | Professional & scientific | 2021 |