| Mclaren Enterprises (Cornwall) Limited | Real estate | 1991 |
| MD Composites Ltd | Extraterritorial | 2025 |
| MD Independent Financial Planning Limited | Financial services | 2013 |
| MD Tailings Consulting Ltd | Professional & scientific | 2024 |
| MDC Projects Limited | Information & communication | 2018 |
| Meakers of Piccadilly Limited | Manufacturing | 2012 |
| Measured Energy Europe Ltd | Professional & scientific | 2013 |
| Medicolegal Midwives Ltd | Professional & scientific | 2023 |
| Medit Salvage (U.K.) Limited | Real estate | 1976 |
| Medusa Audio Tech Ltd | Manufacturing | 2023 |
| Mehras Pishgam Sadra Expo Ltd | Real estate | 2025 |
| Melvin Construction (Cornwall) Limited | Construction | 2015 |
| Melvin Holdings Limited | Construction | 2025 |
| Membly Hall (Falmouth) Limited | Hospitality | 1959 |
| Mepsted Marine Ltd | Manufacturing | 2025 |
| Merchants Manor Limited | Hospitality | 1973 |
| Merchants of the Sun (UK) Ltd | Manufacturing | 2023 |
| Merit Environmental Limited | Construction | 2017 |
| Meyou Holdings Limited | Financial services | 2016 |
| MH Groundworks Limited | Construction | 2013 |
| Michael Bailey Roofing Contractors Ltd | Construction | 2014 |
| Michael Reece Consulting Ltd | Professional & scientific | 2025 |
| Mid-Cornwall Climate and Ecological Hub CIC | Professional & scientific | 2023 |
| Middle Trelan Farm Ltd | Agriculture & fishing | 2024 |
| MIJ Transportation Limited | Transport & logistics | 2020 |
| Milborne Wick Farms Limited | Agriculture & fishing | 1999 |
| Miles Consulting Limited | Information & communication | 2017 |
| Millbrush Limited | Real estate | 2015 |
| Miller and Parker Agriculture Limited | Agriculture & fishing | 2023 |
| Miller Rock Limited | Wholesale & retail | 2017 |
| Millers Garages Limited | Wholesale & retail | 1997 |
| Millers Holdings Limited | Professional & scientific | 2006 |
| Mines a Pasty Limited | Hospitality | 2013 |
| Minsky Trading Limited | Administrative & support | 2018 |
| Miradouro Limited | Real estate | 2023 |
| Miranda Bird Consultancy Limited | Professional & scientific | 2026 |
| Mirror Class Association Limited | Other services | 1983 |
| Mirva Theatre Ltd | Arts & recreation | 2024 |
| Mitchell Communications Ltd | Administrative & support | 2016 |
| MLK Lettings (Cornwall) Ltd | Real estate | 2025 |
| MOD GOD Ltd | Energy | 2020 |
| Modufab PUC Ltd | Manufacturing | 2022 |
| Mona Cove Ltd | Real estate | 2025 |
| Mongrel London Ltd | Wholesale & retail | 2019 |
| MOONROKIT5 Limited | Arts & recreation | 2019 |
| MOR Engineering Ltd | Professional & scientific | 2018 |
| MOR Group Limited | Other services | 2015 |
| Mor&Meadow Ltd | Wholesale & retail | 2025 |
| Mordros Production Ltd | Information & communication | 2024 |
| Morek Engineering Ltd | Professional & scientific | 2019 |
| Morgallos Limited | Energy | 2011 |
| Morgans Falmouth Limited | Wholesale & retail | 2019 |
| Morgawr Ltd | Manufacturing | 2023 |
| Morris Living Ltd | Construction | 2018 |
| Morvah Management Ltd | Professional & scientific | 2022 |
| Morway Ltd | Hospitality | 2025 |
| Moth and Moon Limited | Hospitality | 2015 |
| Motorcycle City Limited | Wholesale & retail | 2021 |
| Mount Pleasant Sustainable Selfbuild Ltd | Construction | 2013 |
| Mountwise Management Limited | Households | 2003 |
| MP Property Developements Limited | Real estate | 2017 |
| Mrgn Holdings Ltd | Financial services | 2017 |
| MRK Stays Ltd | Real estate | 2025 |
| MRS B'S Tearoom Ltd | Hospitality | 2018 |
| MS Retail Stores Ltd | Wholesale & retail | 2018 |
| MSB Cafe Limited | Hospitality | 2022 |
| Mtrs Builders Ltd | Construction | 2018 |
| Muddy Maids Ltd | Education | 2026 |
| Muddy Wellies Gardens Limited | Administrative & support | 2018 |
| Muir Community Insight Ltd | Professional & scientific | 2019 |
| Mulberry Slip Engineering Limited | Construction | 2013 |
| Mutate Development Systems Ltd | Information & communication | 2018 |
| MW Instruments Limited | Real estate | 1981 |
| MW Plant Ltd | Construction | 2020 |
| My Tiny Home Design Ltd | Wholesale & retail | 2017 |
| Mybusinessplan Limited | Professional & scientific | 2013 |
| Mychiro Falmouth Limited | Health & social care | 2023 |
| Mylor Creek Boatyard Ltd | Administrative & support | 2009 |
| Mylor Harbour Limited | Financial services | 2022 |
| Mylor Stores Limited | Wholesale & retail | 2014 |
| Mylor Yacht Club Limited | Arts & recreation | 2021 |
| Myskatonic Ltd | Information & communication | 2020 |
| N3L Limited | Real estate | 2018 |
| Nadyam Properties Limited | Financial services | 2025 |
| Nails 4 U 15 Ltd | Other services | 2023 |
| Nanny Solutions Limited | Administrative & support | 2021 |
| Nansidwell Property Management Limited | Real estate | 2013 |
| Natharcha Limited | Households | 2016 |
| National Solutions UK Ltd | Administrative & support | 2016 |
| Nature Room Cornwall CIC | Health & social care | 2024 |
| Navas Nook LLP | | 2023 |
| Navitaco Ltd | Professional & scientific | 2024 |
| Nclworks Ltd | Professional & scientific | 2017 |
| Neelam Prasad Ltd | Health & social care | 2024 |
| Nekobox Limited | Wholesale & retail | 2025 |
| NEO GEO Consulting Ltd | Mining & quarrying | 2025 |
| Nest Cornwall CIC | Health & social care | 2024 |
| Neurokind Coaching Limited | Administrative & support | 2026 |
| New Bridge Street Holdings Ltd | Real estate | 2025 |
| Newchester Limited | Real estate | 2020 |