| Lighthouse Resorts Ltd | Real estate | 2023 |
| Lighthouse to the Nations | Other services | 2006 |
| Little India Monmouth Ltd | Hospitality | 2025 |
| Littlest Hobos Ltd | Wholesale & retail | 2020 |
| LKP Care Ltd | Health & social care | 2022 |
| Llangattock School Ltd | Education | 2006 |
| Llanrothal Barns Management Company Limited | Households | 2010 |
| Llewellyn Rhys Group Ltd | Financial services | 2023 |
| LMC Property Finance Ltd | Financial services | 2024 |
| Lock Hancocks (Properties) Limited | Real estate | 1985 |
| Lockwood Court Management Limited | Households | 1989 |
| Loddon Park Barn Limited | Real estate | 2017 |
| Loddon Park Farm Estate Limited | Financial services | 2017 |
| Loddon Park Farm Limited | Construction | 2002 |
| Logistics Education Centre Limited | Transport & logistics | 2000 |
| Logoacre Limited | Professional & scientific | 1990 |
| Loose Leads Limited | Administrative & support | 2017 |
| Louis Cull Carpentry & Construction Ltd | Construction | 2022 |
| Love Homeopathy Limited | Health & social care | 2023 |
| Lovell & SON Ltd | Agriculture & fishing | 2012 |
| Lovering Interiors Ltd | Construction | 2017 |
| Lowjinks Limited | Arts & recreation | 2023 |
| Lubas Medical Limited | Health & social care | 2009 |
| Ludus Coffee Co Limited | Wholesale & retail | 2025 |
| Ludus Maximus Ltd | Other services | 2025 |
| Ludus Training Limited | Arts & recreation | 2022 |
| Luna Project Solutions Limited | Construction | 2015 |
| Luxe Moda Designs Limited | Professional & scientific | 2025 |
| M E Stroud Limited | Health & social care | 2011 |
| M F R Planning Limited | Professional & scientific | 2014 |
| M&J Powell Property Ltd | Real estate | 2025 |
| MAC Beard Limited | Hospitality | 2024 |
| Macie Aesthetics Limited | Other services | 2025 |
| Madcaps Hair Company Limited | Other services | 2017 |
| MAG Positive Neurology Limited | Health & social care | 2017 |
| Magmanager Limited | Information & communication | 2015 |
| Make IT Mentoring CIC | Education | 2012 |
| Make Monmouth CIC | Other services | 2021 |
| Mandarin Slate Limited | Wholesale & retail | 1989 |
| Mandarin Stone Holdings Limited | Financial services | 2021 |
| Mandarin Stone Limited | Wholesale & retail | 2015 |
| Manse Business Services Ltd | Education | 2019 |
| Mansfield Developments (South West) Limited | Wholesale & retail | 2008 |
| Manson Associates Limited | Professional & scientific | 2015 |
| Maoz Publishers UK Ltd | Information & communication | 2026 |
| Marc Turley Boiler Services Ltd | Manufacturing | 2022 |
| Margaret Allen Foundation | Education | 1988 |
| Mark a Lewis & Sons Ltd | Construction | 2018 |
| Marmarise Barber Shop 3 Limited | Other services | 2020 |
| Matthew Horwood Photography Ltd | Professional & scientific | 2017 |
| MAX4THERM (UK) Ltd | Wholesale & retail | 2006 |
| Maxi Healthcare Consulting Ltd | Administrative & support | 2023 |
| Maxwell Recruitment Ltd | Administrative & support | 2023 |
| Mccarthy's (Crickhowell) Limited | Other services | 2015 |
| Mccauley Estates Ltd | Real estate | 2024 |
| Mclean Stores Ltd | Wholesale & retail | 2018 |
| Megan Callington Ltd | Other services | 2025 |
| Meikle-Mcintosh Limited | Professional & scientific | 2011 |
| Mentrex Ltd | Health & social care | 2002 |
| Merrivale Accounting Services Limited | Professional & scientific | 2001 |
| Metamorpha Ltd | Information & communication | 2002 |
| MGC Remedial Services Ltd | Construction | 2022 |
| MGS Moto Ltd | Financial services | 2016 |
| MHE Training Resources Ltd | Wholesale & retail | 2018 |
| Miaren Bookkeeping Limited | Professional & scientific | 2009 |
| Michele Down Dynamics Ltd | Other services | 2005 |
| Mike Brokenshire Ltd | Administrative & support | 2021 |
| Mike Warren Mortgage Services Ltd | Financial services | 2024 |
| Milarya Consultancy Ltd | Professional & scientific | 2025 |
| Milk Studios (the Albion) Limited | Administrative & support | 2003 |
| Mill House Creative Consultants Ltd | Manufacturing | 2020 |
| Millbrook Garden Centre Limited | Wholesale & retail | 2014 |
| Millbrook Homes (Cwmbran) Limited | Real estate | 2011 |
| MIM Life Ltd | Health & social care | 2025 |
| Mind Matters Monmouth Limited | Health & social care | 2023 |
| Mindful Thinking Limited | Health & social care | 2025 |
| Miqo Limited | Information & communication | 2023 |
| Missaghi Ltd | Professional & scientific | 2023 |
| MJ Instrument Solutions Limited | Other services | 2016 |
| MJM Electrical (South West) Limited | Construction | 2022 |
| Mobility Installations Limited | Real estate | 2003 |
| Modina Investments Limited | Real estate | 2023 |
| Moko's Mexican Limited | Hospitality | 2005 |
| Momentum Mobility & Rehab Ltd | Wholesale & retail | 2022 |
| Monmouth Day Nursery Limited | Health & social care | 2016 |
| Monmouth & District Rifle Club CIC | Education | 2019 |
| Monmouth and WYE Valley Removals Ltd | Transport & logistics | 2025 |
| Monmouth Appliance Centre Limited | Wholesale & retail | 2016 |
| Monmouth Business Centre Limited | Administrative & support | 2019 |
| Monmouth Canoe & Activity Centre Limited | Arts & recreation | 2007 |
| Monmouth Carpentry and Roofing Ltd | Construction | 2021 |
| Monmouth Clinic Limited | Health & social care | 2021 |
| Monmouth Creed Management Company Limited | Real estate | 2016 |
| Monmouth Electrical Ltd | Construction | 2025 |
| Monmouth Fabrics and Soft Furnishings Ltd | Wholesale & retail | 2018 |
| Monmouth Houseplants Ltd | Wholesale & retail | 2021 |
| Monmouth Masonic Hall Limited | Other services | 2002 |
| Monmouth Masonry Ltd | Construction | 2025 |
| Monmouth MOT Centre Ltd | Wholesale & retail | 2010 |
| Monmouth Moves Limited | Transport & logistics | 2020 |