| Cousins Environmental Consultants Ltd. | Other services | 2000 |
| Cousins Environmental Holdings Ltd. | Real estate | 2002 |
| Crasu Coed CYF | Hospitality | 2021 |
| Crugan Farm Caravan & Camping Ltd | Hospitality | 2014 |
| CU Power Ltd | Manufacturing | 2025 |
| Cumulo Ltd | Financial services | 2019 |
| Cwmni Cliperau CYF | Hospitality | 2010 |
| Cwmni Cydweithredol Cymunedol Tafarn Y FIC Cyfyngedig | Hospitality | 1988 |
| Cwmni SER CYF | Administrative & support | 2016 |
| CWT Crugan Ltd | Wholesale & retail | 2024 |
| CWT Tatws CYF | Wholesale & retail | 2013 |
| Cybi Cyfyngedig | Construction | 2007 |
| Cyfeillion Cadw Tremadog | Information & communication | 1991 |
| Cynhyrchwyr Biff Llyn CYF. | Other services | 1997 |
| D & J Holdings Porthmadog Limited | Professional & scientific | 2012 |
| D Andrews Joinery Limited | Construction | 2017 |
| D E & E M Davies Limited | Agriculture & fishing | 2013 |
| D Howie Ltd | Construction | 2015 |
| D O Evans CYF | Agriculture & fishing | 2018 |
| D W Jones (Plant Hire) Limited | Administrative & support | 2010 |
| D. Davies & Sons Limited | Construction | 2006 |
| D2D Menswear Ltd | Wholesale & retail | 2024 |
| Daliadau I a W CYF | Hospitality | 2021 |
| DAN Haul CYF | Hospitality | 2013 |
| Darlun Home Design Studio CYF | Extraterritorial | 2019 |
| Datmad CYF | Hospitality | 2018 |
| David Cooke (Nantcol) Limited | Manufacturing | 1953 |
| David Roberts Transport Limited | Transport & logistics | 2005 |
| Davies (Cilcoed) CYF | Construction | 2006 |
| DB & E Williams Limited | Construction | 2015 |
| Deintyddfa Deudraeth Dental Care Limited | Health & social care | 2010 |
| Deintyddfa Glandwr CYF | Health & social care | 2014 |
| Derwin Fawr Renewables Ltd | Energy | 2016 |
| Derwydd CYF | Agriculture & fishing | 2016 |
| Designed & Dressed to Impress Consultancy Limited | Professional & scientific | 2022 |
| Dinas Caravan Park and Camping Limited | Hospitality | 2015 |
| Dinas Contracting CYF | Construction | 2011 |
| Dinas DDU Lettings CYF | Hospitality | 2020 |
| Dinbren Shoot Limited | Arts & recreation | 2025 |
| Direct Caravans Ltd | Hospitality | 2002 |
| Dobbers Ltd | Hospitality | 2018 |
| DR & DP Jones Ltd | Agriculture & fishing | 2017 |
| Dragon Drone Surveys & Inspections Limited | Construction | 2026 |
| Dragon Power Services Limited | Construction | 2007 |
| Draig Marine Ltd | Professional & scientific | 2026 |
| Dudodyn Hydro Ltd | Professional & scientific | 2015 |
| Dunn & Ellis CYF | Professional & scientific | 2016 |
| E & G Jones CYF | Agriculture & fishing | 2017 |
| E G Stock Ltd | Agriculture & fishing | 2021 |
| E G Williams Limited | Hospitality | 2015 |
| E H A'I FAB Ynni Adnewyddadol & Trydanol CYF | Construction | 2024 |
| E W Jones (Haulage) Limited | Transport & logistics | 2013 |
| E.Jones Williams and SON Limited | Construction | 1964 |
| Ecopower Advisors Ltd | Professional & scientific | 2023 |
| ED Solutions Psychology Ltd | Health & social care | 2023 |
| EDR Estates Limited | Hospitality | 2002 |
| Edwards Beckett Aviation Ltd | Transport & logistics | 2026 |
| Efsubsea Limited | Agriculture & fishing | 2014 |
| Eiddo AR CYF | Real estate | 2026 |
| Eiddo Derwydd CYF | Real estate | 2024 |
| Eiddo ELC CYF | Real estate | 2005 |
| Eiddo Ffenics Limited | Construction | 2023 |
| Eiddo M.E.L CYF | Financial services | 2023 |
| Eiddo PDU CYF | Real estate | 2017 |
| Eiddo Property Ltd | Real estate | 2025 |
| Eifion Roberts CYF | Agriculture & fishing | 2022 |
| Eifion WYN CYF | Other services | 1991 |
| EJW Properties Limited | Real estate | 2016 |
| Elian Ltd | Real estate | 2000 |
| Elis Llywelyn Williams CYF | Construction | 2022 |
| Elis Williams Developments Limited | Extraterritorial | 2018 |
| Elis Williams Group Limited | Extraterritorial | 2018 |
| Elis Williams Projects Limited | Extraterritorial | 2018 |
| Emmanuel Properties Ltd | Real estate | 2012 |
| EMU Hold Ltd | Real estate | 2022 |
| Emwill Care Limited | Health & social care | 2024 |
| Eric Cullen CYF | Construction | 2004 |
| Erin Samuel Legal Ltd | Professional & scientific | 2021 |
| ERW Fair CYF | Hospitality | 2023 |
| Eryri Eco Construction Limited | Manufacturing | 2018 |
| EW Griffiths CYF | Construction | 2003 |
| Felin Fwyd CYF | Hospitality | 2018 |
| Felin Properties Limited | Real estate | 2015 |
| Ffenestri Dwyfor Windows CYF | Construction | 2004 |
| Fferm Chwilog Fawr CYF | Agriculture & fishing | 2016 |
| Ffermio Metcalfe CYF | Agriculture & fishing | 2025 |
| Ffestiniog Futures Limited | Professional & scientific | 2011 |
| Ffestiniog Railway Holdings Limited | Administrative & support | 1990 |
| Ffridd Hydros Ltd | Construction | 2016 |
| FIN & ES Limited | Hospitality | 2018 |
| Fishy Catch Limited | Agriculture & fishing | 2014 |
| Freya Bentham Ltd | Hospitality | 2017 |
| Furwen Ltd | Agriculture & fishing | 2019 |
| G B Jones Limited | Agriculture & fishing | 2012 |
| G H Griffith A'I Gwmni CYF | Agriculture & fishing | 2016 |
| G Jones Contracts Limited | Construction | 2012 |
| G P Owen Limited | Professional & scientific | 2005 |
| G W Jones Groundworks Ltd | Construction | 2017 |
| G&R Roberts CYF | Agriculture & fishing | 2022 |
| Gabriel Gheorghita Consulting Engineers Ltd. | Professional & scientific | 2009 |