| Lgreggain & Company Limited | Construction | 2002 |
| LIL Perchie Limited | Information & communication | 2026 |
| Lilac Orchard Limited | Wholesale & retail | 1996 |
| Lillydot Limited | Agriculture & fishing | 2023 |
| Lime Tree Heritage Ltd | Construction | 2025 |
| Ling Electrical Ltd | Construction | 2016 |
| Link Scaffolding & Netting Limited | Construction | 2009 |
| Little Jillys Ltd | Hospitality | 2025 |
| Litus Estates Ltd | Real estate | 2024 |
| LJP Enterprises (Maesteg) Limited | Construction | 2018 |
| Lloyd and Pawlett Ltd | Transport & logistics | 2022 |
| Loaded Cuisine Limited | Hospitality | 2023 |
| Locks on Line International Limited | Administrative & support | 2005 |
| Locks on Line Limited | Wholesale & retail | 1999 |
| Locsel Limited | Information & communication | 2006 |
| Lord Nelson Hotel Ltd | Hospitality | 2023 |
| Loretta Fishing Limited | Agriculture & fishing | 2003 |
| Lorex Vans Limited | Manufacturing | 2022 |
| Lorin Ayla Ltd | Hospitality | 2020 |
| LRS Storage Ltd | Transport & logistics | 2024 |
| LSM Pembs Limited | Transport & logistics | 2024 |
| Lunar Wedding Films Ltd | Information & communication | 2021 |
| M & a Engineering Limited | Manufacturing | 2002 |
| M G B Fishing Limited | Agriculture & fishing | 2024 |
| M&S Bridgend Ltd | Real estate | 2026 |
| M&S Pembs Ltd | Transport & logistics | 2020 |
| M&S South Wales Ltd | Transport & logistics | 2024 |
| Mabon Mana & Monsters Ltd | Wholesale & retail | 2026 |
| Mackenzie Corporation Limited | Manufacturing | 2010 |
| Mackenzie International Limited | Manufacturing | 2001 |
| MAD Maintenance Ltd | Manufacturing | 2022 |
| Maerl Ltd | Information & communication | 2012 |
| Maesteg M Limited | Wholesale & retail | 2025 |
| Magic Pump UK Ltd | Wholesale & retail | 2026 |
| Maid in Wales Limited | Administrative & support | 2012 |
| Manderwood Investments Limited | Financial services | 2001 |
| Margam Enterprise Limited | Wholesale & retail | 2017 |
| Marina Bar Neyland Ltd | Hospitality | 2021 |
| Marine Energy (Holdings) Limited | Energy | 2012 |
| Marine Energy Limited | Administrative & support | 2009 |
| Mark Lloyd Setterfield Limited | Extraterritorial | 2024 |
| Mark Whayman Catering Limited | Hospitality | 2018 |
| Mark Wilson & SON Plumbing Limited | Construction | 2025 |
| Mark Wilson Plumbing Limited | Construction | 2016 |
| Martha's Vineyard Ltd | Hospitality | 2018 |
| Marywel Ltd | Financial services | 2024 |
| Matthew Evans Catering Ltd | Hospitality | 2024 |
| Matthew Hobbs Inspection Ltd | Manufacturing | 2022 |
| Matthew Hobbs Inspection Services Limited | Professional & scientific | 2018 |
| Matthews Scaffolding Ltd | Construction | 2024 |
| Maxey's Limited | Hospitality | 2026 |
| Maya Pembs Limited | Construction | 2024 |
| MBK Building and Maintenance Ltd | Construction | 2012 |
| MBK Cleaning Services Limited | Households | 2013 |
| Mccarthy Design & Engineering Co Limited | Professional & scientific | 2012 |
| Mcgee Commercial Ltd | Wholesale & retail | 2023 |
| Mcguires & SON Ltd | Construction | 2024 |
| Melissa Johnson Limited | Arts & recreation | 2009 |
| Mentor P.I.C. Limited | Financial services | 2017 |
| Merlin Autos (Wales) Ltd | Wholesale & retail | 2015 |
| Mertech MER Technical Services Limited | Manufacturing | 2013 |
| MHC (Milford Haven) Limited | Wholesale & retail | 2015 |
| Mhpa RBS Trustee Company Limited | Financial services | 2013 |
| Mhwp Limited | Administrative & support | 2012 |
| Miles Drainage & Groundworks Limited | Construction | 2019 |
| Miles Plant Hire Limited | Administrative & support | 2014 |
| Milford Gymnastics Academy Ltd | Arts & recreation | 2013 |
| Milford Haven Golf Club Limited | Arts & recreation | 1943 |
| Milford Haven Hand Car Wash Ltd | Administrative & support | 2024 |
| Milford Haven Masonic Hall Company Limited(The) | Real estate | 1906 |
| Milford Haven Properties Limited | Energy | 2011 |
| Milford Waterfront Resort Limited | Hospitality | 2021 |
| Milford Yacht Brokerage Limited | Professional & scientific | 2003 |
| Milford-Shiny Car Wash Ltd | Administrative & support | 2025 |
| MIN Y MÔR - Pembrokeshire Ltd | Education | 2025 |
| MJ Production Services Ltd | Professional & scientific | 2020 |
| MJ Recycling Limited | Water & waste | 2017 |
| ML HV Service Ltd | Construction | 2021 |
| MLH Engineering Ltd | Construction | 2016 |
| Monster Motorcycles Limited | Wholesale & retail | 2015 |
| Morgan Richards Electrical Ltd | Construction | 2026 |
| MR GS Mobile Tyres Ltd | Wholesale & retail | 2026 |
| MS Morrissey Ltd | Administrative & support | 2024 |
| Mselone Limited | Professional & scientific | 2022 |
| MTH Property Ltd | Real estate | 2015 |
| Munn & Co Properties Ltd | Real estate | 2025 |
| Murray Crescent House Management Company Ltd | Households | 2021 |
| Musselwick Management Limited | Wholesale & retail | 2018 |
| My Taxi Pembrokeshire Ltd | Transport & logistics | 2026 |
| Myrtle Meadows (Steynton) Management Limited | Households | 2017 |
| Nach Properties Ltd | Real estate | 2024 |
| Natalie Absalom Aesthetics Ltd | Other services | 2025 |
| Nautico's Ltd | Hospitality | 2023 |
| Naylor Carpentry & Building Development Ltd | Construction | 2023 |
| NCS Properties Ltd | Real estate | 2024 |
| Nelson Accommodation Limited | Hospitality | 2025 |
| NER Food Ltd | Hospitality | 2025 |
| Nessie's at Haverhub Limited | Hospitality | 2026 |
| Netlet Properties Ltd | Administrative & support | 2016 |
| New Brighton Properties Limited | Real estate | 2001 |