| Lighting Integration Ltd | Manufacturing | 2015 |
| Liliwen Fach Home Care Ltd | Health & social care | 2025 |
| Liljo Interiors Ltd | Construction | 2014 |
| Lilywhite Accountancy Ltd | Professional & scientific | 2021 |
| Limerock Group Ltd | Financial services | 2018 |
| Limerock Holdings Ltd | Real estate | 2018 |
| Limerock Property Solutions Ltd | Construction | 2018 |
| Lindsay Thorne Solicitors Limited | Professional & scientific | 2007 |
| Linear Planning & Design Services Limited | Professional & scientific | 2020 |
| Liners, Bags & Sacks Limited | Wholesale & retail | 2010 |
| Link AV Limited | Professional & scientific | 2002 |
| Lion Guard Installations Ltd | Construction | 2025 |
| Liquid Floor Screed (Wales) Limited | Construction | 2013 |
| Liron Ltd | Extraterritorial | 2022 |
| Livefree Adventures Limited | Administrative & support | 2021 |
| LJS Law Ltd | Professional & scientific | 2022 |
| LK Skin & Beauty Clinic Ltd | Other services | 2025 |
| Lladnar Holdings Limited | Financial services | 2020 |
| Llandeilo Bakers Limited | Manufacturing | 2012 |
| Llanelli and District Shopmobility | Administrative & support | 2011 |
| Llanelli and Mynydd Mawr Railway Company Limited | Transport & logistics | 1999 |
| Llanelli Barber Ltd | Other services | 2024 |
| Llanelli Engineering Limited | | 1980 |
| Llanelli Flooring Supplies Ltd | Wholesale & retail | 2018 |
| Llanelli Gate Management Company Limited | Real estate | 2011 |
| Llanelli Gymnastics Club Ltd | Arts & recreation | 2015 |
| Llanelli Hand Car Wash Ltd | Wholesale & retail | 2026 |
| Llanelli Indoor Bowling Club Ltd | Arts & recreation | 2023 |
| Llanelli Meat Limited | Hospitality | 2023 |
| Llanelli Mind | Health & social care | 2015 |
| Llanelli Properties & Rentals Ltd | Real estate | 2021 |
| Llanelli Railway Goods Shed Trust | Arts & recreation | 2011 |
| Llanelli Reds AFC Limited | Arts & recreation | 2018 |
| Llanelli Regeneration Ltd | Construction | 2024 |
| Llanelli RFC Limited | Arts & recreation | 2003 |
| Llanelli Steelers Basketball Club Ltd | Arts & recreation | 2025 |
| Llanelli Town AFC Limited | Arts & recreation | 2024 |
| Llanelli Wanderers Limited | Arts & recreation | 2024 |
| Llanelli Wanderers Players Limited | Extraterritorial | 2024 |
| Llanelli Wanderers RFC Limited | Arts & recreation | 2017 |
| Llanelli Wanderers Rugby Limited | Extraterritorial | 2024 |
| Llanelly House Trust Ltd. | Arts & recreation | 2003 |
| Llesiant Delta Wellbeing Ltd | Administrative & support | 2018 |
| Lloyd & Gravell Employee Ownership Trustee Limited | Professional & scientific | 2026 |
| Lloyd & Gravell Limited | Construction | 1998 |
| Lloyds Leisure Limited | Arts & recreation | 2023 |
| Llwyddiant Success UK Akanchawa Ltd | Transport & logistics | 2024 |
| Llwyn Country Accommodation Limited | Hospitality | 2023 |
| Llwynhendy Stores Limited | Wholesale & retail | 2015 |
| Llwynifan Farm Caravan Site Ltd | Hospitality | 2011 |
| LM Financial Planning Limited | Financial services | 2020 |
| Loaves & Fish UK CIC | Education | 2025 |
| Local Studio Ltd | Other services | 2025 |
| Lockspot Ltd. | Administrative & support | 2017 |
| Lockspot Management Ltd. | Information & communication | 2018 |
| Loft Logic Ltd | Administrative & support | 2023 |
| Logic Document Archiving Limited | Administrative & support | 2011 |
| Lolek Limited | Wholesale & retail | 2006 |
| London Hub Fashion Limited | Wholesale & retail | 2012 |
| Lone Wolf Operations Limited | Financial services | 2020 |
| Long Oaks Court (Management) Limited | Households | 1989 |
| Loud Applause Productions Ltd | Other services | 2011 |
| LR Electrics Limited | Manufacturing | 2018 |
| LRA Logistics Limited | Transport & logistics | 2019 |
| LSH Investments Ltd | Real estate | 2019 |
| LTL Propertys Ltd | Real estate | 2022 |
| Lucem Aesthetics Limited | Manufacturing | 2014 |
| Lukasz Pedrycz Transport Ltd. | Transport & logistics | 2015 |
| Lush Lettings Ltd | Real estate | 2015 |
| Luther Lewis Estates Limited | Real estate | 1999 |
| LUX Energy (Wind) Limited | Administrative & support | 2014 |
| LV Convenience Stores Ltd | Wholesale & retail | 2023 |
| LWT Design Services Limited | Professional & scientific | 2022 |
| Lynx Workshop | Health & social care | 2010 |
| M & a Convenience Stores Limited | Wholesale & retail | 2019 |
| M and R Plastering Limited | Construction | 2025 |
| M C Plumbing & Heating Services Limited | Construction | 2023 |
| M F Styles Stock & Agri Services Ltd | Agriculture & fishing | 2020 |
| M H Jones Accountancy Ltd | Professional & scientific | 2023 |
| M Hiorns Building Contractor Limited | Construction | 2002 |
| M&M (West Wales) Properties Ltd | Real estate | 2021 |
| M21 Properties Ltd | Real estate | 2022 |
| M3 Property Group Ltd | Real estate | 2025 |
| M4 Trailers Limited | Manufacturing | 2008 |
| MA Spice House Limited | Hospitality | 2024 |
| Machynys Leisure Limited | Financial services | 2022 |
| Machynys Peninsula Golf & Country Club Limited | Arts & recreation | 2004 |
| Maclachlan Holdings Ltd | Real estate | 2026 |
| Maclachlan Properties Ltd | Real estate | 2025 |
| Macrocymru CYF | Information & communication | 2022 |
| Made Easy Investments Limited | Real estate | 2024 |
| Maesllech Holdings Ltd | Agriculture & fishing | 2018 |
| Maesycastell Holdings Limited | Financial services | 2026 |
| Magic Memory Photos (Llanelli) Ltd | Professional & scientific | 2026 |
| Magmatrix UK Ltd | Wholesale & retail | 2021 |
| Magpie Builders Cymru Ltd | Construction | 2025 |
| Main Decoration Limited | Extraterritorial | 2022 |
| Main Dryline Limited | Construction | 2009 |
| MAKERSMATRIX3DDESIGN Ltd | Manufacturing | 2025 |
| Makewebwork Ltd | Information & communication | 2024 |