| Mooney Farms Ltd | Agriculture & fishing | 2020 |
| Moonshell (UK) Ltd | Professional & scientific | 2025 |
| Moor Road Business Park Limited | Extraterritorial | 2007 |
| Moore & Dunwoody, Limited | Real estate | 1943 |
| Moore Project Mangement Company Limited - the | Households | 2005 |
| Moorfield Court Kilkeel Management Limited | Households | 2010 |
| Morahin Developments Limited | Administrative & support | 2014 |
| More Creative Enterprises Ltd | Wholesale & retail | 2023 |
| Moremma Offshore Ltd | Transport & logistics | 2026 |
| Morgan Telematics Ltd | Wholesale & retail | 1994 |
| Morgan Transport Services Limited | Transport & logistics | 2020 |
| Moriarty BIM Ltd | Professional & scientific | 2024 |
| Morlea Ltd | Construction | 2016 |
| Morreal Ltd | Real estate | 2020 |
| Morris Duncan Marine Ltd | Agriculture & fishing | 2011 |
| Morris Fresh Produce Ltd | Wholesale & retail | 2015 |
| Morrissey Investments Limited | Construction | 2013 |
| Morton Distribution Services Ltd | Transport & logistics | 2019 |
| Mosat Management LP | | 2017 |
| Moscow Freight Limited | Transport & logistics | 2013 |
| Moss Gate Properties Limited | Real estate | 2014 |
| Moth & Mink Ltd | Manufacturing | 2023 |
| Motis CS Limited | Real estate | 2018 |
| Motis Estates Limited | Real estate | 2017 |
| Motis Group Limited | Financial services | 2017 |
| Motis Pallet Services Ltd | Manufacturing | 2015 |
| Motis Technology Limited | Information & communication | 2026 |
| Motis Tolls Limited | Administrative & support | 2014 |
| Mount Kearney Quarries & Contracts Ltd | Mining & quarrying | 2020 |
| Mountain View Management Company (N.I.) Ltd | Households | 2012 |
| Mountain Ways Ireland Ltd | Administrative & support | 2018 |
| Mountainpole Properties (UK) Limited | Financial services | 2025 |
| Mountainview Commercial Property Ltd | Real estate | 2017 |
| Mourne Air Ltd | Professional & scientific | 2017 |
| Mourne Assets Limited | Construction | 2025 |
| Mourne Bathrooms & Tiles Ltd | Professional & scientific | 2008 |
| Mourne Breakers Ltd | Wholesale & retail | 2016 |
| Mourne Casuals Limited | | 1998 |
| Mourne Civils Ltd | Construction | 2024 |
| Mourne Commercials Ltd | Wholesale & retail | 2023 |
| Mourne Composts Limited | Manufacturing | 1986 |
| Mourne Conservation Graziers Ltd | Real estate | 2023 |
| Mourne Consulting Limited | Information & communication | 2022 |
| Mourne Contract Services Limited | Construction | 2018 |
| Mourne Country Park Limited | Real estate | 1997 |
| Mourne Craft Ltd | Construction | 2020 |
| Mourne Diner Ltd | Hospitality | 2023 |
| Mourne Eggs Limited | Wholesale & retail | 2016 |
| Mourne Engineering Solutions Ltd | Professional & scientific | 2023 |
| Mourne Firewood Supplies Limited | Wholesale & retail | 2023 |
| Mourne Flight Training Ltd | Education | 2024 |
| Mourne Food & Drink Ltd | Wholesale & retail | 2021 |
| Mourne Food Distribution Limited | Hospitality | 2026 |
| Mourne Form Ltd | Extraterritorial | 2024 |
| Mourne Freight Services Ltd | Transport & logistics | 2014 |
| Mourne Gateway Glamping Limited | Extraterritorial | 2023 |
| Mourne Glamping Pods Ltd | Hospitality | 2018 |
| Mourne Grange Management Company Limited | Households | 2005 |
| Mourne Granite Quarries Limited | Administrative & support | 1937 |
| Mourne Hall Apartments Management Company Limited | Households | 1996 |
| Mourne Hydraulic Hose and Fittings Ltd | Manufacturing | 1989 |
| Mourne Leak Finders Ltd | Construction | 2018 |
| Mourne Livestock Ltd | Agriculture & fishing | 2022 |
| Mourne Luxury Glamping Ltd | Hospitality | 2021 |
| Mourne Meitheal CIC | Administrative & support | 2023 |
| Mourne Moves Ltd | Real estate | 2024 |
| Mourne Neurodiversity Practice Ltd | Health & social care | 2026 |
| Mourne Office Supplies Limited | Wholesale & retail | 2007 |
| Mourne Peak Ltd | Wholesale & retail | 2026 |
| Mourne Private Clinic Ltd | Real estate | 2023 |
| Mourne Properties & Developments Limited | Construction | 2005 |
| Mourne Property Investments Ltd | Real estate | 2025 |
| Mourne Property Ltd | Real estate | 2005 |
| Mourne Ridge Properties Ltd | Construction | 2025 |
| Mourne Scan Clinic Ltd | Health & social care | 2016 |
| Mourne Seafood Cookery School Ltd | Hospitality | 2011 |
| Mourne Spares Ltd | Wholesale & retail | 2026 |
| Mourne Textiles Limited | Manufacturing | 1958 |
| Mourne Tile Distribution Ltd | Construction | 2023 |
| Mourne Timber Frame Ltd | Construction | 2021 |
| Mourne Timber Solutions Limited | Wholesale & retail | 2011 |
| Mourne Touring Limited | Hospitality | 2018 |
| Mourne Training Services Limited | Other services | 2016 |
| Mourne Tyre Services Ltd | Wholesale & retail | 2018 |
| Mourne Valley Foods Limited | Wholesale & retail | 2018 |
| Mourne Vehicle Sales Ltd | Wholesale & retail | 2024 |
| Mourne Weavers Limited | Manufacturing | 2013 |
| Mourne Windows and Doors Limited | Extraterritorial | 1998 |
| Mournehill Windows Limited | Manufacturing | 1998 |
| Mourneview Service Station Ltd | Wholesale & retail | 2020 |
| Mowhan Developments Ltd | Construction | 2020 |
| Moyad Ltd | Wholesale & retail | 2022 |
| Moyadd Farm Limited | Agriculture & fishing | 2017 |
| Moygannon Consulting Limited | Information & communication | 2013 |
| Moygannon Court Limited | Households | 1986 |
| Moygannon Garden Centre Ltd | Wholesale & retail | 2013 |
| Moygannon Landscaping Limited | Professional & scientific | 2013 |
| Moyglass Investments Limited | Real estate | 2005 |
| Moyo Marketing Services Ltd | Wholesale & retail | 2023 |
| Moyola Holdings Limited | Wholesale & retail | 2022 |