| Williams of Solva Limited | Real estate | 2000 |
| Williams Pet & Garden Supplies Ltd | Wholesale & retail | 2026 |
| Williams Primary Care Solutions Limited | Health & social care | 2007 |
| Williams Property Lettings Ltd | Real estate | 2025 |
| Williams Ventilation Limited | Manufacturing | 2012 |
| Willingale Interiors Ltd | Wholesale & retail | 2018 |
| Willis Legal Services Limited | Administrative & support | 2002 |
| Willis Sales & Installations Ltd | Construction | 2022 |
| Willow Court Apartments Management Services Limited | Professional & scientific | 2003 |
| Willow Court Development Phase 1 Limited | Extraterritorial | 2003 |
| Willow Court Village Holdings Ltd | Financial services | 2025 |
| Willow Court Village Limited | Professional & scientific | 2003 |
| Willow Farm Property Limited | Construction | 2020 |
| Willow Properties Swansea Limited | Real estate | 2025 |
| Willow White Ltd | Financial services | 2021 |
| Willows Pre-School Limited | Education | 2008 |
| Wills Advice Bureau Ltd | Hospitality | 2011 |
| Willz Property Developments Ltd | Real estate | 2016 |
| Wilma's Walls Limited | Real estate | 2017 |
| Wimozee Technology Ltd. | Wholesale & retail | 2025 |
| Wincanton MOT Centre Ltd | Professional & scientific | 2020 |
| Winch WEN Industrial Estate Management Company Limited | Real estate | 2004 |
| Wind Street Hair Ltd | Other services | 2019 |
| Wind Street Kebab & Pizza Ltd | Hospitality | 2025 |
| Wind Turbine Engineering UK Limited | Information & communication | 2020 |
| Windlesham Enterprises Limited | Manufacturing | 2008 |
| Windmill Forest Limited | Real estate | 2021 |
| Windowmaker Ltd | Manufacturing | 2018 |
| Windrush Cymru Elders CIC | Education | 2026 |
| Windslade House Management Limited | Real estate | 2004 |
| Windsor Cafe (Swansea) Limited | Hospitality | 1951 |
| Windsor Court Residents Association (Swansea)Limited | Households | 1964 |
| Windsor Gardens Management Company Limited | Administrative & support | 2007 |
| Windsor Glass & Glazing Co Ltd. | Manufacturing | 1989 |
| Winly Ltd | Administrative & support | 2017 |
| Winnie Underhill Ltd | Hospitality | 2022 |
| Winnings K6 Limited | Professional & scientific | 2015 |
| Winstone Trading UK Limited | Construction | 2024 |
| Winstonian Construction Services Ltd | Construction | 2020 |
| Winwales Limited | Professional & scientific | 2004 |
| Wipe OUT Creations Limited | Other services | 2018 |
| Wirral Medical Services Limited | Health & social care | 2022 |
| Wisdom House Academy Ltd | Construction | 2012 |
| Wisdom House Swansea Ltd | Construction | 2026 |
| Wisdom Lettings Limited | Real estate | 2024 |
| Wise Bellies Limited | Manufacturing | 2024 |
| Wise Cheema Ltd | Hospitality | 2023 |
| WISE4WORK Ltd | Professional & scientific | 2014 |
| Wishbones Body Therapies Limited | Health & social care | 2025 |
| Wishtree Homes Ltd | Real estate | 2021 |
| Wisterya Ltd | Households | 2021 |
| With Heart Ltd | Administrative & support | 2019 |
| Witherswood Limited | Education | 2005 |
| Within Group Limited | Professional & scientific | 2021 |
| Wiwer Limited | Wholesale & retail | 2015 |
| WJC Engineering Services Ltd | Manufacturing | 2019 |
| Wjhc Limited | Education | 2016 |
| WJP Subsea Solutions Limited | Professional & scientific | 2014 |
| WJS Accountancy Services Ltd | Financial services | 2022 |
| Wkzk Limited | Real estate | 2021 |
| WLD Distribution Ltd | Wholesale & retail | 2024 |
| Wldstore Ltd | Wholesale & retail | 2026 |
| WLL Civils Ltd | Agriculture & fishing | 2008 |
| WM Retail Limited | Hospitality | 2018 |
| WMA Cardiff Ltd | Administrative & support | 2025 |
| WNE Group Ltd | Wholesale & retail | 2022 |
| WNI Limited | Other services | 2023 |
| WOK Express Swansea Fast Food Limited | Hospitality | 2024 |
| Wokway Ltd | Hospitality | 2019 |
| Wokway Street Kitchen Ltd | Hospitality | 2025 |
| Wolf Garden Rooms Ltd | Manufacturing | 2024 |
| Wolfestone Holdings Limited | Professional & scientific | 2014 |
| Wolfestone Translation Ltd | Professional & scientific | 2006 |
| Wolffather Limited | Wholesale & retail | 2024 |
| Women Beyond Cancer CIC | Health & social care | 2025 |
| Women in Sustainability Network Ltd | Information & communication | 2018 |
| Women's AID Federation of England | Health & social care | 1996 |
| Women's Community Skating Ltd | Arts & recreation | 2026 |
| Women’S Romany- Gyspy Empowerment Network CIC | Information & communication | 2026 |
| Wood Energy Limited | Manufacturing | 2001 |
| Wood Memorial Benches Limited | Manufacturing | 2011 |
| Woodhaze Limited | Health & social care | 2009 |
| Woodland Hideaway Glynarthen Ltd | Hospitality | 2022 |
| Woodlands Developments (South Wales) Limited | Construction | 1988 |
| Woodlands UK Property Ltd | Real estate | 1999 |
| Woodlock Holdings Limited | Manufacturing | 1981 |
| Woodly Furniture Limited | Manufacturing | 2026 |
| Woodmasters Limited | Extraterritorial | 1993 |
| Woodridge Court Management Company Limited | Households | 2003 |
| Woodrow's Coffee Ltd | Hospitality | 2024 |
| Woodstone Installation Services Ltd | Construction | 2010 |
| Woodys Construction Ltd | Construction | 2018 |
| Woolcock Holdings Ltd | Professional & scientific | 2015 |
| Work LAB Limited | Professional & scientific | 2012 |
| Work Wild Limited | Professional & scientific | 2016 |
| Workforce Home Improvements Ltd | Manufacturing | 2025 |
| Workgearuk Ltd | Extraterritorial | 2019 |
| Working Star Limited | Professional & scientific | 2022 |
| Workrest Blades Limited | Manufacturing | 2007 |
| World Bioprotection Forum Ltd | Professional & scientific | 2019 |