| MR Tech GUY Limited | Professional & scientific | 2019 |
| MRJ Filipino Delights Limited | Hospitality | 2025 |
| MRL Management Consultants Limited | Professional & scientific | 2008 |
| MRN Constructions Ltd | Other services | 2019 |
| MRO145 Ltd | Manufacturing | 2024 |
| Mrpg Holdings Ltd | Financial services | 2025 |
| MRS Wrinkles Ltd | Information & communication | 2024 |
| MRS. Butterworth's Productions Limited | Information & communication | 2021 |
| MS Motorsport Solutions Limited | Professional & scientific | 2024 |
| MS Paint Ltd | Manufacturing | 2025 |
| MS Sunny Co., Ltd | Extraterritorial | 2013 |
| MS7ANAESTHEISA Ltd | Health & social care | 2026 |
| MSA Homes Limited | Real estate | 2019 |
| Msarimk Ltd | Extraterritorial | 2024 |
| Mscnatmanangement Ltd | Professional & scientific | 2025 |
| MSD General Trading Co., Ltd | Wholesale & retail | 2023 |
| Msdl Engineering Ltd | Manufacturing | 2023 |
| Msjc UK Ltd | Construction | 2020 |
| MSO Contractors Ltd | Construction | 2018 |
| MSO Helicopter Transports Ltd | Transport & logistics | 2024 |
| Mspore Global Ltd | Wholesale & retail | 2023 |
| MST Consulting Ltd | Manufacturing | 2025 |
| MT Asset Surveys Ltd | Professional & scientific | 2023 |
| MT Cambridge Limited | Health & social care | 2019 |
| MT Energy Solutions Ltd | Professional & scientific | 2025 |
| MT Groundworks (East Anglia) Ltd | Construction | 2015 |
| MTC Engineering (Cambridge) Ltd | Professional & scientific | 2013 |
| MTK Aviation Ltd | Manufacturing | 2023 |
| MTO International Trading Co., Ltd | Wholesale & retail | 2021 |
| MTS - Mati Ltd | Manufacturing | 2020 |
| MU Beta Ltd | Information & communication | 2013 |
| Mubarak Market Ltd | Wholesale & retail | 2026 |
| Much Scan Services Limited | Public administration | 2024 |
| Muddy Machines Ltd | Professional & scientific | 2020 |
| Mudhut Communication Limited | Professional & scientific | 2005 |
| Muhe Market Research Limited | Information & communication | 2025 |
| Muir & Kerr Limited | Other services | 2008 |
| Mukhi Mart Ltd | Wholesale & retail | 2025 |
| Mulberry Carpentry & Construction Limited | Construction | 2018 |
| Mulberry Close (Leys Road Cambridge) Residents Society Limited | Real estate | 1963 |
| Mulberry Holdings Cambridge Limited | Financial services | 2018 |
| Mulberry House Software Limited | Information & communication | 2017 |
| Mulberry Place (Saffron Walden) Management Company Limited | Households | 2015 |
| Mullins & Stedman Ltd | Construction | 2018 |
| Multi Chain International Trade Limited | Wholesale & retail | 2025 |
| Multi Services Comp Ltd | Manufacturing | 2024 |
| Multi-Dimensional Solutions Limited | Professional & scientific | 2021 |
| Multipay Group Limited | Financial services | 2020 |
| Multiplai Health Ltd | Professional & scientific | 2020 |
| Multiplifi Ltd | Professional & scientific | 2026 |
| Multnomah Advisory Limited | Professional & scientific | 2026 |
| Mumin Import and Export Co., Ltd | Wholesale & retail | 2020 |
| Mumo.Ko Ltd | Real estate | 2019 |
| Munday Educational Consultancy Ltd | Professional & scientific | 2024 |
| Mundibiopharma Limited | Wholesale & retail | 2014 |
| Mundipharma International Limited | Professional & scientific | 1992 |
| Mundipharma International Services Limited | Administrative & support | 2012 |
| Mundipharma International Technical Operations Limited | Professional & scientific | 2017 |
| Mundipharma IT Services Limited | Information & communication | 2011 |
| Mundipharma Medical Company Limited | Wholesale & retail | 2014 |
| Mundipharma Regulatory Limited | Professional & scientific | 2025 |
| Mundipharma Research Limited | Professional & scientific | 2002 |
| Munro Group Limited | Real estate | 2002 |
| Munro Holdings (Cambridge) Limited | Professional & scientific | 2015 |
| Munro Leisure Investments Ltd. | Hospitality | 1996 |
| Munteanu Constantin Bogdan(Ten) Ltd | Manufacturing | 2023 |
| Muradal Ltd | Information & communication | 2015 |
| Murfin Motor Company Ltd | Wholesale & retail | 2006 |
| Murmac Properties Limited | Construction | 2018 |
| Murray Edwards Conferences Limited | Hospitality | 1999 |
| Mursal Global Ltd | Wholesale & retail | 2026 |
| Mursla Limited | Professional & scientific | 2017 |
| Musculoskeletal Injury Care Ltd | Health & social care | 2026 |
| Musenium Ltd | Wholesale & retail | 2025 |
| Museum of Cambridge | Arts & recreation | 1946 |
| Mushal Limited | Wholesale & retail | 2026 |
| Music Will Save the World Ltd | Professional & scientific | 2024 |
| Musk Co., Ltd | Wholesale & retail | 2020 |
| Muslim Cultural Insight Ltd | Professional & scientific | 2018 |
| Muslim Family Adventures Ltd | Education | 2021 |
| Mustang Topco Limited | Financial services | 2023 |
| Mustard Tech Limited | Information & communication | 2025 |
| Muyu Home Property Limited | Real estate | 2025 |
| Muzinest Ltd | Real estate | 2025 |
| MV Inspections Ltd | Manufacturing | 2025 |
| Mv-Transformations Ltd | Education | 2024 |
| MVF Advisory Ltd | Professional & scientific | 2025 |
| MVK Property Investment Limited | Real estate | 2023 |
| MVP Advisory Services Limited | Professional & scientific | 2022 |
| MW Cambridge Ltd | Professional & scientific | 2010 |
| MW Family AT1 Ltd | Real estate | 2022 |
| MW Locksmiths Ltd | Other services | 2025 |
| MW Personal Fitness Ltd | Arts & recreation | 2024 |
| Mwanaka Fresh Farm Foods Limited | Agriculture & fishing | 2025 |
| Mwifa (Holdings) Limited | Professional & scientific | 2009 |
| Mwiri Old Boys Association United Kingdom (Moba UK) | Education | 2023 |
| MWP Medical Ltd | Health & social care | 2022 |
| My Baby (Cambridgeshire) Ltd | Wholesale & retail | 2025 |
| My Baby Store Ltd | Wholesale & retail | 2025 |
| My Health Integral Ltd | Information & communication | 2024 |