| Webbs Property Limited | Professional & scientific | 1958 |
| WEBNINJA360 Limited | Agriculture & fishing | 2023 |
| Welsh Dragon Coal Limited | Wholesale & retail | 1996 |
| Welsh Hills Bakery Limited | Manufacturing | 2014 |
| Welsh Valley Antiques Limited | Wholesale & retail | 2026 |
| Werfa Investment Limited | Construction | 2024 |
| Wern DEG Ltd | Real estate | 2025 |
| Wesmec Limited | Construction | 2023 |
| Westernet Limited | Information & communication | 2017 |
| WG Roofing & Building Ltd | Construction | 2026 |
| What (Neath) Ltd | Wholesale & retail | 2023 |
| Wickk Ltd | Wholesale & retail | 2021 |
| Willheat Limited | Construction | 2011 |
| Williams Bros. Electrical (Llwydcoed) Limited | Wholesale & retail | 1996 |
| Williams Commercial Properties Limited | Real estate | 2016 |
| Willowchem Technology Limited | Manufacturing | 2006 |
| Wilson Body Repairs Limited | Wholesale & retail | 2017 |
| Wilson Oral Health Limited | Health & social care | 2017 |
| Wingdit Ltd | Hospitality | 2023 |
| WLP WUL Ltd | Hospitality | 2026 |
| Woodland Homes South Wales Limited | Construction | 2005 |
| Woodlands Procurement Ltd | Professional & scientific | 2023 |
| Xavy Limited | Information & communication | 2026 |
| Y Ddraig Goch Travel Group Ltd | Administrative & support | 2025 |
| Ymarfer Cymru Limited | Arts & recreation | 2004 |
| Ynys View Community Hub Limited | Arts & recreation | 2014 |
| YR Catering Limited | Hospitality | 2015 |
| Zebra Squared Marketing Ltd | Professional & scientific | 2023 |
| Zelgo Limited | Other services | 2016 |
| Zenergise Limited | Wholesale & retail | 2024 |
| Zim&Scotts Ltd | Transport & logistics | 2026 |