| Campfa Ffau'R Llewod Ltd | Arts & recreation | 2026 |
| Campio Rhydolion CYF | Hospitality | 2022 |
| Canolfan Felin Fach Centre Limited | Health & social care | 1996 |
| Capel Carmel | Other services | 2018 |
| Capel Salem Arts Limited | Arts & recreation | 2025 |
| Capel Salem CYF | Arts & recreation | 2025 |
| Carafanau Porthdinllaen CYF | Hospitality | 2019 |
| Carl Kammerling International Limited | Wholesale & retail | 1963 |
| Carreg Gwalch CYF | Wholesale & retail | 2000 |
| Cartrefi Llŷn CYF. | Real estate | 2017 |
| Castellmarch CYF | Hospitality | 2017 |
| Castwell Limited | Wholesale & retail | 1994 |
| CBR Safety Services Ltd | Construction | 2014 |
| Celtic Heat Packs Ltd | Manufacturing | 2024 |
| Celtic Heritage Reclaimed Stone Products Ltd | Manufacturing | 2025 |
| Cerebral Soup Limited | Professional & scientific | 2008 |
| Cerrig Granite & Slate Limited | Manufacturing | 2010 |
| Certivue Limited | Extraterritorial | 2008 |
| Charlotte Pinnington Interiors Limited | Professional & scientific | 2025 |
| Check My PAY Ltd | Professional & scientific | 2017 |
| Check Your PAY Ltd | Professional & scientific | 2024 |
| CHI a FI CYF | Health & social care | 2025 |
| Chilli Penguin Stoves Ltd | Manufacturing | 2017 |
| Chitexo Limited | Professional & scientific | 2024 |
| Chrono Quest Ltd | Wholesale & retail | 2016 |
| CIG Cerion Meats Ltd | Manufacturing | 2012 |
| CIM Caravan Storage CYF | Transport & logistics | 2020 |
| CIM Farm Caravan and Camping CYF | Hospitality | 2020 |
| CK Food and Drinks Limited | Manufacturing | 2012 |
| Clannad Ltd | Construction | 2024 |
| Clarendon Food Company Limited(The) | Manufacturing | 1980 |
| Clnik 94 Limited | Health & social care | 2024 |
| Clover Locums Limited | Health & social care | 2014 |
| Clwb Hwylio Pwllheli Sailing Club CYF | Administrative & support | 1960 |
| Cmnuk Limited | Information & communication | 2018 |
| Coastal Cabs (Abersoch) Ltd | Transport & logistics | 2021 |
| Coastal Learning and Lifestyle Services Ltd | Other services | 2025 |
| Coed Coch Farms Ltd | Agriculture & fishing | 2016 |
| Coedlan CYF | Hospitality | 2010 |
| Colin Dobson Roofing CYF | Construction | 2012 |
| Continuum Media Network UK Limited | Information & communication | 2018 |
| Cosy Nest Management Ltd | Administrative & support | 2025 |
| Cottage Court Limited | Real estate | 2018 |
| Courthill Business Consultants Limited | Professional & scientific | 2022 |
| Criccieth Arts Association Cymdeithas Celfyddydau Criccieth | Arts & recreation | 1988 |
| Cromwell Services NW Ltd | Construction | 2022 |
| Crossroads Retreats | Health & social care | 2006 |
| Cwmni Arian CYF | Financial services | 2020 |
| Cwmni Gwaeth Cyfyngedig | Information & communication | 2017 |
| Cwmni Nant Cyfyngedig | Hospitality | 2016 |
| Cwmni Plas Glyn - Y - Weddw Limited | Arts & recreation | 1994 |
| Cwrw Llyn CYF | Manufacturing | 2010 |
| Cwtch@Hafod Ltd | Hospitality | 2017 |
| Cyfeillion Eglwys Llandegwning | Arts & recreation | 2002 |
| Cyfeillion HEN Ysgol Llangwnnadl | Professional & scientific | 2004 |
| Cyfle Llyn CYF | Professional & scientific | 2026 |
| Cyfle Support Services CYF | Administrative & support | 2005 |
| Cymru Muzic Cyfyngedig | Information & communication | 2001 |
| Cynan Consulting Limited | Professional & scientific | 2017 |
| Cynan CYF | Real estate | 2008 |
| Cynlas Groundworks Limited | Construction | 2024 |
| Cysgu Llwynog CYF | Hospitality | 2017 |
| Cyson CYF | Professional & scientific | 2020 |
| D & L Williams CYF | Construction | 2017 |
| D & R Williams Ltd | Construction | 2016 |
| D Marc Jones Limited | Construction | 2019 |
| D&P Electrical (Abersoch) Limited | Energy | 2011 |
| D. Jones Decorators Limited | Construction | 2007 |
| Dafad DDU CYF | Administrative & support | 2018 |
| Daffodil Foods Limited | Manufacturing | 2011 |
| Dafydd Lloyd Limited | Construction | 2012 |
| DAN DO Gwynedd CYF | Real estate | 2024 |
| Dave Group Ltd | Construction | 2023 |
| David Fawcett (Design) Limited | Manufacturing | 1976 |
| David Fawcett Limited | Manufacturing | 2022 |
| David James Properties Ltd | Real estate | 2025 |
| Davies A'I Gwmni CYF | Agriculture & fishing | 2024 |
| Davies-Hughes & Sons Limited | Manufacturing | 2017 |
| DDS Rentals Limited | Real estate | 2015 |
| Deri Davies Cigydd-Butchers Limited | Wholesale & retail | 2022 |
| Derwen Llyn Construction Limited | Construction | 2015 |
| Deucoch Touring & Camping Park Limited | Hospitality | 2020 |
| DIGWYDDIADAU8EVENTS Limited | Arts & recreation | 2017 |
| Discover Llŷn Ltd | Administrative & support | 2022 |
| Distracted Ltd | Professional & scientific | 2023 |
| DJ Williams Electrical Limited | Construction | 2015 |
| DJH Construction Group Ltd | Construction | 2025 |
| Doodson Limited | Hospitality | 2015 |
| DP Jones Electrical Limited | Construction | 2018 |
| Dragon Baker. Limited | Manufacturing | 2025 |
| Dragon Civil Engineering Limited | Construction | 1998 |
| Dragon Detailing & Body Repairs Ltd | Wholesale & retail | 2026 |
| Dragon Signs NW Limited | Manufacturing | 2022 |
| Drws Agored CYF. | Professional & scientific | 2002 |
| DWR Water Solutions Ltd | Construction | 2026 |
| Dwyfor Coffee Company Limited | Wholesale & retail | 1995 |
| Dyffryn Heating Ltd | Construction | 2022 |
| Dylan M Williams Adeiladwr CYF | Construction | 2023 |
| E Consultants Ltd | Professional & scientific | 2024 |
| E P L Soccer & Sports Tours Limited | Arts & recreation | 2007 |