| Swansea Volkswagen Centre Limited | Wholesale & retail | 2023 |
| Swansea Watch Repair Centre Limited | Other services | 2026 |
| Swansea Watersports Ltd | Arts & recreation | 2014 |
| Swansea West Maintenance Ltd | Professional & scientific | 2026 |
| Swansea West Roofing & Scaffolding Limited | Construction | 2023 |
| Swansea West Scaffolding Ltd | Construction | 2023 |
| Swansea Women's AID | Health & social care | 2022 |
| Swansea Ymca | Real estate | 2013 |
| Swansea.Co.Uk Limited | Extraterritorial | 2021 |
| Swansea.Com Holdings Limited | Financial services | 2004 |
| Swansea.Com Investments Five Limited | Extraterritorial | 2024 |
| Swansea.Com Investments Limited | Financial services | 2023 |
| Swansea.Com Investments Three Limited | Real estate | 2024 |
| Swansea.Com Investments Two Limited | Real estate | 2020 |
| Swansea.Com Ltd | Professional & scientific | 2016 |
| SWANSEA1969 Limited | Hospitality | 2025 |
| SWANSEA4STUDENTS Ltd | Real estate | 2013 |
| Swanseabus Ltd | Transport & logistics | 2009 |
| Swansid Ltd | Construction | 2021 |
| Swanswell Close Management Limited | Administrative & support | 2004 |
| Swasea.Marine.Supplys Ltd | Agriculture & fishing | 2025 |
| Sway Road Car Sales Ltd | Wholesale & retail | 2015 |
| Sway Road Motor Vehicles Limited | Wholesale & retail | 2024 |
| SWC Balustrades Ltd | Construction | 2024 |
| Sweeeties Limited | Wholesale & retail | 2025 |
| SWEEP2023 Ltd | Real estate | 2023 |
| Sweet Nutriitionals Limited | Administrative & support | 2026 |
| Sweet Peeps Ltd | Wholesale & retail | 2024 |
| Sweetheart Photography Ltd | Professional & scientific | 2026 |
| Sweetiedreamz Ltd | Wholesale & retail | 2021 |
| Swerdna Coldstores Ltd | Transport & logistics | 2024 |
| Swerdna Group Holdings Ltd | Financial services | 2023 |
| Swerdna Medical & Service Limited | Transport & logistics | 2023 |
| Swerdna Mobile Assets Limited | Administrative & support | 2023 |
| Swerdna Transport Ltd | Transport & logistics | 2016 |
| Swift Curry Ltd | Hospitality | 2020 |
| Swift Electrical and Construction Ltd | Construction | 2025 |
| Swim Wales | Arts & recreation | 2003 |
| Swish Fulfilment and Storage Ltd | Administrative & support | 2023 |
| Swish Fulfilment Ltd | Administrative & support | 2018 |
| Switch Connect Limited | Professional & scientific | 2025 |
| Swlr Ltd | Manufacturing | 2004 |
| Swmedicare Limited | Health & social care | 2018 |
| SWN Y MOR Properties Ltd | Real estate | 2021 |
| Swn-Y-Môr Rental Limited | Hospitality | 2024 |
| Sworld Consult Ltd | Information & communication | 2011 |
| SWS Certification Holdings Limited | Financial services | 2024 |
| SWT (Cardiff) Limited | Administrative & support | 2012 |
| Swwroc Limited Limited | Other services | 2020 |
| SY Salon Ltd | Other services | 2020 |
| Sykma Limited | Real estate | 2024 |
| Symlec Electrical Services Ltd | Construction | 2015 |
| Symorgh Holdings Ltd | Real estate | 2025 |
| Symphotech Event Safety Limited | Public administration | 2011 |
| Symple Ltd | Wholesale & retail | 2022 |
| Synatherm Limited | Manufacturing | 2015 |
| Syncro Civils Ltd | Construction | 2019 |
| Synergy Wealth Management Limited | Financial services | 2009 |
| Synser Ltd | Wholesale & retail | 2021 |
| Systemlogic Limited | Information & communication | 2003 |
| Systems Electrical Engineering Limited | Other services | 1993 |
| Systems UN Limited | Extraterritorial | 2023 |
| SZB Legal Ltd | Professional & scientific | 2022 |
| SZB Legal Services Ltd | Professional & scientific | 2020 |
| Szwed Reinforcement Systems Ltd | Construction | 2025 |
| T & G GAS Services Ltd | Construction | 2022 |
| T & J Autos Ltd | Wholesale & retail | 2010 |
| T & K Precision Scaffolding Ltd | Construction | 2019 |
| T & M (Scaffolding) Limited | Construction | 2005 |
| T & M Building Contractors Limited | Construction | 2002 |
| T & M Facilities Ltd | Other services | 2021 |
| T B Holiday Lets Ltd | Hospitality | 2014 |
| T Best Leader Limited | | 2016 |
| T Day Holdings Ltd | Real estate | 2021 |
| T Dorosti Limited | Health & social care | 2026 |
| T Ecommerce Ltd | Wholesale & retail | 2023 |
| T G Jones & Associates Limited | Administrative & support | 2016 |
| T Healing G Ltd | Health & social care | 2026 |
| T Nails Ltd | Other services | 2020 |
| T Price Lettings Ltd | Real estate | 2021 |
| T Stevens & SON Limited | Other services | 2017 |
| T W K Thomas & SON Limited | Wholesale & retail | 1999 |
| T W Rees Property Ltd | Real estate | 2026 |
| T&L Premier Travel Limited | Transport & logistics | 2020 |
| T&M Engineering Solutions UK Ltd | Professional & scientific | 2026 |
| T&M Group Holdings Ltd | Financial services | 2025 |
| T&M Group Ltd | Construction | 2007 |
| T&M Property Ltd | Real estate | 2018 |
| T&T Roofing & Home Improvements Ltd | Construction | 2026 |
| T&Y Associates Ltd | Health & social care | 2017 |
| T. J. Brown Ltd | Construction | 2025 |
| T. M. Owen & SON Limited | Construction | 2002 |
| T.A. Shore Company Limited | Manufacturing | 2004 |
| T.C Treasures Limited | Wholesale & retail | 2026 |
| T.D. Stores Limited | Wholesale & retail | 2010 |
| T.J.Evans & SON. Ltd. | Construction | 2014 |
| T.J.Plumbing & Heating Services Limited | Construction | 2018 |
| T.K. Beynon Limited | Wholesale & retail | 1987 |
| T.M Technical Consultant Limited | Professional & scientific | 2022 |
| T.M. Wiberg Limited | Wholesale & retail | 2002 |