| Grey Property Investments Ltd | Real estate | 2023 |
| Grey Property Sourcing Ltd | Administrative & support | 2023 |
| Greyfriars Estate (Preston) Limited | Financial services | 1950 |
| Greyline Executive Limited | Professional & scientific | 2026 |
| Gridsail Limited | Real estate | 2003 |
| Gridwise DNO Services Ltd | Professional & scientific | 2024 |
| Griffiths CS Limited | Information & communication | 2025 |
| Griffiths GAS Ltd | Administrative & support | 2019 |
| Griffiths Waste Management Ltd | Water & waste | 2010 |
| Gril&L Ltd | Hospitality | 2026 |
| Grindsmith Holdings Limited | Financial services | 2015 |
| Gringo Imports (U.K.) Limited | Wholesale & retail | 1993 |
| Grizzle & Bourke Ltd | Professional & scientific | 2020 |
| GRJ Property Co. Limited | Real estate | 2019 |
| Gro-Org Ltd | Wholesale & retail | 2016 |
| Groesffordd Homes Ltd | Construction | 2019 |
| Ground Rent Holdings Limited | Real estate | 2024 |
| Grounded Trees Ltd | Administrative & support | 2017 |
| Groundswell Dance Company | Arts & recreation | 2000 |
| Group Developments Ltd | Construction | 2024 |
| Grove Construction Management Ltd | Professional & scientific | 2024 |
| Grove Inc Ltd | Wholesale & retail | 2022 |
| Grove Nanomaterials Limited | Professional & scientific | 2018 |
| Grove Property (Wales) Limited | Construction | 2006 |
| Groves Avenue Management Limited | Real estate | 1997 |
| Grow Art & Lifestyle Ltd | Manufacturing | 2022 |
| Grow Outside C.I.C. | Health & social care | 2016 |
| Growbrick Developments Ltd | Construction | 2004 |
| Growbrick Holdings Limited | Construction | 2011 |
| Growbrick Limited | Real estate | 2001 |
| Growing Places Swansea Limited | Agriculture & fishing | 2018 |
| GRS MCR Ltd | Manufacturing | 2017 |
| Grub Hub Swansea Limited | Hospitality | 2024 |
| Gruvly Music Ltd | Wholesale & retail | 2023 |
| GRW FCA Limited | Administrative & support | 2010 |
| GS Artists Swansea | Wholesale & retail | 2018 |
| GS Technical Publications Ltd | Information & communication | 2015 |
| GSA Projects UK Ltd | Administrative & support | 2014 |
| GSB Property (Swansea) Limited | Real estate | 2026 |
| GSC Software Solutions Limited | Information & communication | 2025 |
| GSF Property Developments Limited | Real estate | 2019 |
| GSM Enterprises Ltd | Wholesale & retail | 2019 |
| GSW & SON Limited | Construction | 2025 |
| GT IT Ltd | Public administration | 2021 |
| GT Media & Management Ltd | Arts & recreation | 2026 |
| GT Mobility Limited | Wholesale & retail | 2002 |
| GT Motor Factors Wales Ltd | Wholesale & retail | 2023 |
| GT Swansea Limited | Hospitality | 2024 |
| GTB Transport Service Limited | Transport & logistics | 2025 |
| Gtox Ltd | Professional & scientific | 2021 |
| Gttf CIC | Information & communication | 2023 |
| Guap International Ltd | Information & communication | 2015 |
| Guardian Edge Ltd | Administrative & support | 2017 |
| Guardian Global Tech Ltd | Information & communication | 2026 |
| Guardian Property Services (Gpsuk) Limited | Manufacturing | 2019 |
| Guardianpro Mouthguards Ltd | Manufacturing | 2014 |
| Guerilla Fitness Ltd | Arts & recreation | 2015 |
| Guerilla Holdings Ltd | Other services | 2025 |
| Guerilla Property Group Limited | Real estate | 2019 |
| Gugz N Oaks Ltd | Other services | 2019 |
| Guided Finances Ltd | Professional & scientific | 2024 |
| Guided Spirits Ltd | Professional & scientific | 2026 |
| Guiding Wellness Limited | Health & social care | 2019 |
| Guizhouren Ltd | Hospitality | 2025 |
| Guizhourenculture Ltd | Wholesale & retail | 2025 |
| Gulsh Properties Ltd | Real estate | 2025 |
| GUM Blitzer Ltd | Water & waste | 2012 |
| Gumball Machine (Restoration) Ltd | Wholesale & retail | 2023 |
| Gurdeepsm Limited | Information & communication | 2015 |
| Guruji Enterprise Ltd | Real estate | 2022 |
| GUS Quantity Surveying Ltd | Professional & scientific | 2019 |
| Gusto Design Limited | Professional & scientific | 2003 |
| Guts Surfboards Limited | Wholesale & retail | 2011 |
| GV Thornhill Ltd | Real estate | 2019 |
| GW Administration Ltd | Administrative & support | 2019 |
| GW Specialist Render Systems Ltd | Construction | 2024 |
| Gwabb Technologies Limited | Manufacturing | 2009 |
| Gwalia Property Solutions Ltd | Real estate | 2020 |
| Gwaun Clawdd Limited | Other services | 2024 |
| Gwen Properties Ltd | Households | 2024 |
| Gwenlais Farm Holdings Limited | Real estate | 2023 |
| Gwern Estates Limited | Construction | 1947 |
| GWL Roofing & Scaffolding Ltd | Construction | 2024 |
| Gwlad Consulting Limited | Information & communication | 1998 |
| Gworks Limited | Construction | 2002 |
| Gwrhyd Services Ltd | Construction | 2020 |
| Gwydr Upholstery Limited | Manufacturing | 2002 |
| Gwyl Coda Cyfyngedig | Arts & recreation | 2018 |
| Gwylfa Care and Transport Ltd | Health & social care | 2025 |
| Gwyn Davies Carpentry Limited | Construction | 2005 |
| Gwyn Faen Developments Ltd | Construction | 2024 |
| Gwynt Ffinnant Ltd | Agriculture & fishing | 2016 |
| Gwyr Anaesthesia Ltd | Health & social care | 2013 |
| Gwyr Community Land Trust Limited | Construction | 2023 |
| Gwyr Developments Ltd | Construction | 2020 |
| Gwyr Limited | Other services | 2017 |
| Gynaecology Care Limited | Health & social care | 2025 |
| Gyrru Marketing Limited | Professional & scientific | 2024 |
| Gyvan Total Care Ltd | Health & social care | 2020 |
| H & H Building Renovation Services Ltd | Professional & scientific | 2016 |