| Rubbertech Limited | Manufacturing | 2006 |
| Ruthin & Denbigh Gymnastics Club Ltd | Arts & recreation | 2016 |
| Ruthin Artisan Markets CIC | Administrative & support | 2020 |
| Ruthin Castle Estates Ltd | Hospitality | 2013 |
| Ruthin Castle Hotel Ltd | Hospitality | 2014 |
| Ruthin Dental Practice Limited | Health & social care | 2022 |
| Ruthin Farmers Auction Company Limited | Other services | 1920 |
| Ruthin Laundry Ltd | Other services | 2019 |
| Ruthin Precast Concrete Limited | Manufacturing | 1996 |
| Ruthin Restaurant Limited | Hospitality | 2020 |
| Ruthin Stockbrokers & Investment Management Limited | Financial services | 2013 |
| Ruthin Town FC Ltd | Arts & recreation | 2024 |
| Ruthin Tree Care Ltd | Administrative & support | 2023 |
| Ruthinpub&Co Limited | Hospitality | 2025 |
| RVE Roofing Ltd | Construction | 2024 |
| S P Kell Ltd | Professional & scientific | 2013 |
| S.W Paramount Consulting Limited | Professional & scientific | 2012 |
| SA Davenham Services Limited | Administrative & support | 2017 |
| Salisbury Garden & Hire Services Ltd | Manufacturing | 2016 |
| Sapphire Streams Limited | Health & social care | 1987 |
| Scott House Limited | Professional & scientific | 1989 |
| Seiont Limited | Mining & quarrying | 2016 |
| Seren Solutions Limited | Real estate | 2021 |
| Seven Oaks Ruthin Limited | Real estate | 2023 |
| Sidan Cafe Ltd | Hospitality | 2025 |
| Siop Gymunedol Pwllglas Community Shop | Wholesale & retail | 2011 |
| Sirius Business Transformation Limited | Professional & scientific | 2005 |
| Skillsology Ltd | Education | 2026 |
| SKIN22 Aesthetics Ltd | Other services | 2022 |
| Smiths Direct Ltd | Wholesale & retail | 2024 |
| Soil and Soul Ltd | Extraterritorial | 2024 |
| Solar North Limited | Other services | 2021 |
| Solar NOW Limited | Construction | 2021 |
| Spinnaker Business Solutions Limited | Professional & scientific | 2020 |
| SQM Storage Ltd | Real estate | 2021 |
| STAGE1ENERGY Ltd | Information & communication | 2026 |
| Sterlingsafe Trustee Company Limited | Administrative & support | 2011 |
| Strudel & Dragon Consulting Ltd | Other services | 2015 |
| Stylee Network Solutions Limited | Information & communication | 2025 |
| Summerwell Developments Limited | Construction | 2003 |
| Supair Cymru Ltd | Arts & recreation | 2023 |
| Sustainable Trade Supplies Ltd | Wholesale & retail | 2026 |
| Swift Energy Solutions (NW) Ltd | Construction | 2018 |
| Swift Pest Control Limited | Agriculture & fishing | 2007 |
| Swlh Ltd | Real estate | 2019 |
| Synergize 24 Hours Limited | Information & communication | 2022 |
| Tabor Training Services Ltd | Education | 2014 |
| Tanis Property Ltd | Real estate | 2026 |
| Tartan Computer Training Ltd | Information & communication | 2001 |
| Tax by Return Limited | Professional & scientific | 2019 |
| Terian Computer Services Limited | Information & communication | 1983 |
| THE Brewer Community Limited | Professional & scientific | 2011 |
| THE Brewer Group (Wales) Limited | Professional & scientific | 2011 |
| THE Building Plot Limited | Professional & scientific | 2017 |
| THE Crown PUB and Campsite Limited | Hospitality | 2021 |
| THE Crucial Marketing Company Limited | Professional & scientific | 2009 |
| THE Energy Company (UK) Ltd | Professional & scientific | 2004 |
| THE Energy Company Limited | Professional & scientific | 1998 |
| THE Feeder (North) Ltd | Other services | 2018 |
| THE Goodman and Ruthin Charity | Health & social care | 2008 |
| THE GUT Health Dietitian Ltd | Health & social care | 2025 |
| THE Hide Ruthin NW Ltd | Hospitality | 2025 |
| THE Leyland Arms Ltd | Hospitality | 2021 |
| THE Mill Child Care Centre Limited | Health & social care | 2003 |
| THE Mill Childcare Limited | Financial services | 2025 |
| THE Oliver James Gardening Company Limited | Administrative & support | 2015 |
| THE Tax Academy C.I.C. | Professional & scientific | 2014 |
| The-Look Ltd | Administrative & support | 2022 |
| Theatr Gadair DDU Ltd | Education | 2019 |
| Thomas Farms (PYG) Ltd | Agriculture & fishing | 2026 |
| Three Feathers Limited | Hospitality | 2013 |
| Through the Gate Limited | Education | 2017 |
| Through the Gate Services C.I.C. | Administrative & support | 2024 |
| TIM W Jones CYF | Professional & scientific | 2019 |
| Toms Teeth Limited | Health & social care | 2022 |
| Town Mill Ruthin Management Company Limited | Hospitality | 1989 |
| Tracey Lavinia Designs Limited | Arts & recreation | 2020 |
| Traffic Sense Limited | Professional & scientific | 2000 |
| Trail Wolf Ltd | Manufacturing | 2024 |
| Treadlight Forestry Limited | Wholesale & retail | 2014 |
| Trefor Jones (Ruthin) Limited | Wholesale & retail | 1979 |
| Trosnant Care Home Ltd | Health & social care | 2025 |
| Trustworthy Artificial Intelligence Limited | Information & communication | 2025 |
| Turnaround Solutions Limited | Administrative & support | 2006 |
| Turner Bros Developments Ltd | Construction | 2008 |
| TY Architecture Cyfyngedig | Professional & scientific | 2015 |
| TY Famau Retreats Limited | Hospitality | 2018 |
| Ty'N Y Mynydd Farm Ltd | Agriculture & fishing | 2024 |
| Tyddyn Lantern Limited | Construction | 2024 |
| U.K Discovery Health Ltd | Administrative & support | 2022 |
| Union Wrestling Ltd | Arts & recreation | 2023 |
| Unity Creative Limited | Professional & scientific | 2012 |
| Urbanbuild ( Special Projects ) Limited | Construction | 2004 |
| Urbanbuild (Northern) Limited | Construction | 2007 |
| Urbanbuild Limited | Construction | 2003 |
| V1 Property Development Limited | Hospitality | 2016 |
| Vale Golf Centre Limited | Arts & recreation | 2021 |
| Vale Groundworks & Construction Ltd | Construction | 2020 |
| Vale Veterinary Chemicals Limited | Professional & scientific | 2024 |
| Vale Veterinary Equipment Limited | Professional & scientific | 2022 |