| SUB Electrical Ltd | Construction | 2016 |
| Submate Ltd | Information & communication | 2026 |
| Subsurface Analytics Ltd | Information & communication | 2026 |
| Success House Limited | Health & social care | 2018 |
| SUD Enterprises Ltd | Wholesale & retail | 2018 |
| Sudivya Ltd | Wholesale & retail | 2012 |
| Sufai Ltd | Information & communication | 2025 |
| Suits and Software Ltd | Information & communication | 2026 |
| Sullaire Limited | Other services | 2020 |
| Sullivans Estate Agents Ltd | Real estate | 2022 |
| Sullivans Sales & Lettings Ltd | Real estate | 2015 |
| Sultan Car Sales Ltd | Wholesale & retail | 2023 |
| Sultan Restaurant Swansea Ltd | Hospitality | 2025 |
| SUM Watt Ltd | Professional & scientific | 2012 |
| SUM YAO Limited | Wholesale & retail | 2024 |
| Summer Place 1962 Limited | Extraterritorial | 2014 |
| Summerland Property Holdings Ltd | Real estate | 2018 |
| Summers Abroad Limited | Education | 2004 |
| Summit Good CIC | Education | 2019 |
| Sumsiaz Ltd | Wholesale & retail | 2023 |
| Sun Thai Limited | Hospitality | 2023 |
| Sunkissed Beauty & Tanning Ltd | Other services | 2019 |
| Sunlight Garden Ltd | Wholesale & retail | 2014 |
| Sunni Skin Ltd | Wholesale & retail | 2025 |
| Sunny Works Ltd | Professional & scientific | 2025 |
| Sunnybrook Homes Ltd | Real estate | 2024 |
| Sunnyside Autos (Gorseinon) Limited | Wholesale & retail | 2002 |
| Sunplants Limited | Construction | 1988 |
| Sunset Bay Ltd | Hospitality | 2007 |
| Sunset Capital Group Ltd | Financial services | 2026 |
| Sunset Group Limited | Health & social care | 2016 |
| Sunshine Living Property Ltd | Real estate | 2026 |
| Sunshine Palace Limited | Hospitality | 2025 |
| Sunshine Properties (SW) Limited | Real estate | 2023 |
| SUP Wales Limited | Wholesale & retail | 2017 |
| Supdudes Ltd | Wholesale & retail | 2021 |
| Super BIO Boost CIC | Financial services | 2023 |
| Super Hand Car-Wash (Swansea) Ltd | Administrative & support | 2024 |
| Super Pizza Swansea Ltd | Hospitality | 2024 |
| Super Trench Direct Limited | Construction | 2023 |
| Super-Fix PM Ltd | Other services | 2023 |
| Superior Computers Limited | Other services | 2009 |
| Superior Redevelopment Ltd | Real estate | 2022 |
| Supermost Entertainments Limited | Information & communication | 1977 |
| Superworld Entertainments Limited | Arts & recreation | 1981 |
| Supplements UN Limited | Extraterritorial | 2023 |
| Supply Houses Group Limited | Real estate | 2024 |
| Supplylife Group Limited | Health & social care | 2018 |
| Support for Neurodiversity Ltd | Wholesale & retail | 2024 |
| Support Matters Swansea Ltd | Health & social care | 2025 |
| Supreme Ceilings & Carpentry Ltd | Construction | 2008 |
| Supreme Express Cleaning Limited | Administrative & support | 2011 |
| Supreme Online Retail Limited | Wholesale & retail | 2024 |
| Supreme PVC Swansea Ltd | Construction | 2025 |
| Surecare Travel Limited | Transport & logistics | 2018 |
| Surefire Distribution Ltd | Construction | 2013 |
| Sureview Holdco Limited | Financial services | 2023 |
| Sureview Holdings Limited | Administrative & support | 2019 |
| Sureview Systems Limited | Administrative & support | 2019 |
| Surf Therapy CIC | Education | 2019 |
| Surfability UK CIC | Arts & recreation | 2013 |
| Surfside Properties Limited | Real estate | 2013 |
| Surgical Wisdom Limited | Health & social care | 2015 |
| Surgicare Group Ltd | Health & social care | 2021 |
| Sustainability Risk Solutions Ltd | Professional & scientific | 2024 |
| Sustainability Risk Solutions Services Ltd | Professional & scientific | 2024 |
| Sustainable Accountant Limited | Administrative & support | 2020 |
| Sustainable Eco Houses Limited | Real estate | 2024 |
| Sustainable Recycling Concepts Limited | Other services | 2019 |
| Susu Trading Limited | Wholesale & retail | 2009 |
| Suwad Limited | Hospitality | 2018 |
| Suzy Bailey Limited | Health & social care | 2023 |
| SVG Promotions Limited | Administrative & support | 2013 |
| SVM Entreprises Ltd | Transport & logistics | 2016 |
| SVM Management Ltd | Real estate | 2012 |
| SVS Technology Limited | Administrative & support | 2019 |
| SW Block Management Limited | Real estate | 2023 |
| SW Info SEC Ltd | Information & communication | 2025 |
| SW Luxury Cars Limited | Real estate | 1977 |
| SW Property 1 Ltd | Real estate | 2025 |
| SW Scaffolding (Carmarthen) Ltd | Construction | 2023 |
| Swalek Ltd | Manufacturing | 2013 |
| Swalek Real Estate Ltd | Real estate | 2024 |
| Swallowcraft Limited | Households | 1988 |
| Swan Alloy UK Ltd. | Manufacturing | 1996 |
| Swan Auto Design Ltd | Wholesale & retail | 2022 |
| Swan Barber Ltd | Other services | 2024 |
| Swan Catering Ltd | Wholesale & retail | 2022 |
| Swan CD Limited | Manufacturing | 2004 |
| Swan Consulting Limited | Professional & scientific | 2002 |
| Swan Grill Ltd | Hospitality | 2018 |
| Swan Letting Limited | Real estate | 2016 |
| Swan Media Ltd | Information & communication | 2019 |
| Swan Mortgages Ltd | Financial services | 2020 |
| Swan Roofing Ltd | Construction | 2025 |
| Swan Scaffolding Ltd | Construction | 2014 |
| Swan Spice Ltd | Hospitality | 2019 |
| Swan Tailors Ltd | Manufacturing | 2022 |
| Swan TV Community Interest Company | Information & communication | 2022 |
| Swan Tyres Limited | Wholesale & retail | 2025 |