| CUT Master Hairs Style Ltd | Other services | 2019 |
| CW Engineering Specialists Limited | Manufacturing | 2025 |
| CWM Cloch Hydro Limited | Energy | 2013 |
| CWM Cloch MCJ Hydro Ltd | Energy | 2021 |
| Cwmni a FO BEN BID Bont CYF | Administrative & support | 2025 |
| Cwmni Beddgelert CYF | Other services | 1997 |
| Cwmni Canolfan YR Aelwyd Caernarfon CYF. | Arts & recreation | 2001 |
| Cwmni Cyhoeddi Gwynn Cyfyngedig | Information & communication | 1981 |
| Cwmni Cymuned Clynnog Community Company CYF. | Real estate | 2000 |
| Cwmni DA (Ymddiriedolwr) CYF | Financial services | 2018 |
| Cwmni DA CYF | Information & communication | 1994 |
| Cwmni Egino Limited | Construction | 2021 |
| Cwmni Engedi 2.0 CYF. | Education | 2021 |
| Cwmni Gwynant CYF. | Real estate | 2001 |
| Cwmni Melin CYF | Professional & scientific | 2025 |
| Cwmni Murmur Company CYF | Arts & recreation | 2017 |
| Cwmni Rheoli YR AFR CYF | Hospitality | 2024 |
| Cwrw DA CYF | Wholesale & retail | 2013 |
| Cwrw Ogwen CYF | Manufacturing | 2016 |
| Cwtch Digital Ltd | Information & communication | 2026 |
| Cwtin CBC | Arts & recreation | 2024 |
| Cyhoeddiadau'R Stamp CYF. | Information & communication | 2020 |
| Cymdeithas Rheilffordd Eryri | Transport & logistics | 1996 |
| Cymen Cyfyngedig | Professional & scientific | 1994 |
| Cymen Holdings Limited | Professional & scientific | 2007 |
| Cyngor AR Bopeth Conwy Gwynedd Citizens Advice | Information & communication | 2002 |
| Cynlas CYF | Professional & scientific | 2015 |
| Cywaith Cyfyngedig | Extraterritorial | 2010 |
| D & M Fencing and Groundworks Contractors Ltd | Construction | 2024 |
| D G Jones & SON Ltd | Construction | 2015 |
| D S Roberts Properties Ltd | Real estate | 2026 |
| D. M. M. Engineering Limited | Manufacturing | 1982 |
| D.G. Jones Limited | Construction | 2002 |
| D.R. Williams (Felinwnda) Limited | Construction | 1976 |
| Daffodil Group Ltd | Other services | 2024 |
| Daffodil Trading Ltd | Other services | 2023 |
| Dafydd Bulman Limited | Health & social care | 2020 |
| DAN Hipkiss Coaching Ltd | Arts & recreation | 2021 |
| Danani Hotels Ltd | Hospitality | 2018 |
| Darganfodol Ltd | Education | 2024 |
| Darlun CYF. | Information & communication | 2014 |
| DAT Hairdress Ltd | Other services | 2021 |
| Datarf Cyfyngedig | Real estate | 2008 |
| Datblygiadau Egni Gwledig C.B.C | Professional & scientific | 2014 |
| Datrys Consulting Engineers Limited | Professional & scientific | 2002 |
| Datyn Limited | Information & communication | 2020 |
| Davbuckconstruction Limited | Construction | 2020 |
| David Garth Limited | Construction | 2020 |
| David Hale & Sons Ltd | Construction | 2012 |
| Davies Evens Jones Ltd | Wholesale & retail | 2004 |
| Dawns I Bawb | Arts & recreation | 2005 |
| Dawson Hale Salisbury Ltd | Financial services | 2020 |
| Dealt Solutions Ltd | Wholesale & retail | 2021 |
| Debbidoo Limited | Professional & scientific | 2008 |
| Decorative Stone Supplies Ltd | Manufacturing | 2023 |
| Deilen CIC | Education | 2024 |
| Delight Training Services Limited | Other services | 2000 |
| Delivery Solutions (Delsol) Limited | Transport & logistics | 2003 |
| Delsol International Limited | Transport & logistics | 2023 |
| Delwedd Ltd | Information & communication | 2016 |
| Designer Signs North Wales Ltd | Manufacturing | 2012 |
| Digital Community Limited | Information & communication | 2005 |
| DJ Group Waterproofing Limited | Construction | 2024 |
| DJ Roof Test.Uk Ltd | Professional & scientific | 2023 |
| DMM International Limited | Wholesale & retail | 1986 |
| Dmmwales Group Limited | Manufacturing | 1995 |
| Dodrefn Perkins Furniture Limited | Wholesale & retail | 2000 |
| Dolydd Cars Limited | Wholesale & retail | 2025 |
| Domdent Limited | Health & social care | 2015 |
| Dorothea Greener Camping Limited | Hospitality | 2025 |
| Dough Ball Catering Ltd | Hospitality | 2023 |
| DPL Hygiene Supplies (UK) Limited | Administrative & support | 2009 |
| DR Gwion Williams CYF | Health & social care | 2016 |
| Draenog CYF | Professional & scientific | 2022 |
| Dragon Motors (CWM Y GLO) Ltd | Wholesale & retail | 2014 |
| Dragon Tech Ltd | Information & communication | 2022 |
| Draig Security & Safety CYF | Administrative & support | 2008 |
| Drainserv Ltd | Water & waste | 2023 |
| DSK Media Ltd | Administrative & support | 2017 |
| DWJ Property Management Ltd | Real estate | 2024 |
| Dwyfor Oils Limited | Wholesale & retail | 2007 |
| Dwylo DA CYF | Education | 1994 |
| Dwylo Saff C.I.C. | Health & social care | 2025 |
| Dylan Morgan CYF | Other services | 2016 |
| Dysgu Henbant CIC | Education | 2025 |
| E P Teflons Limited | Construction | 2011 |
| E W & H Williams & Sons (Aggregates) Limited | Wholesale & retail | 2011 |
| E W & H Williams & Sons (Agriculture) Limited | Agriculture & fishing | 2011 |
| E W & H Williams & Sons (Engineering Services) Limited | Manufacturing | 2011 |
| E W & H Williams & Sons (Haulage) Limited | Transport & logistics | 2011 |
| E W & H Williams & Sons (Holdings) Limited | Transport & logistics | 2011 |
| E&E LET Ltd | Real estate | 2025 |
| E.H.P. Limited | Real estate | 2011 |
| Easybooks International Ltd | Extraterritorial | 2022 |
| ECM Associates Limited | Professional & scientific | 2005 |
| Eco Green Heating Ltd | Construction | 2010 |
| Eco Green to Clean Ltd | Administrative & support | 2025 |
| Ecostrategy LS Ltd | Wholesale & retail | 2025 |
| Eden Gardening Company Ltd | Arts & recreation | 2022 |
| Edgar JOS Developments Ltd | Construction | 2025 |