| Deliverease Limited | Transport & logistics | 2024 |
| Deliveries UN Limited | Extraterritorial | 2013 |
| Delsion Ltd | Administrative & support | 2015 |
| Delta V Creative Ltd | Information & communication | 2025 |
| DELTA1POINT5 Limited | Construction | 2024 |
| Deltoid Consulting Limited | Information & communication | 2013 |
| Delur Haus Limited | Real estate | 2022 |
| Delux DECOR8 (MCR) Ltd | Other services | 2018 |
| Deluxe Hygiene Ltd | Manufacturing | 2023 |
| Delwyn Griffiths CYF | Financial services | 2003 |
| Demaskas Limited | Other services | 2008 |
| Dementia Knights Limited | Extraterritorial | 2025 |
| Demir Electrical Limited | Construction | 2019 |
| Denali Advanced Integration Europe Limited | Administrative & support | 2017 |
| Dennis Barber (Pontardawe) Ltd | Other services | 2025 |
| Denny's Magic Diners UK Limited | Hospitality | 2017 |
| Dentzen Locum Ltd | Health & social care | 2020 |
| Denware Limited | Information & communication | 2018 |
| Derek Thomas Builders Limited | Wholesale & retail | 2007 |
| Derlwyn Holdings Ltd | Financial services | 2023 |
| Derwen Consulting Limited | Professional & scientific | 2026 |
| Derwen Fawr Anaesthesia Limited | Health & social care | 2019 |
| Derwen Fawr Properties Limited | Real estate | 2004 |
| Derwen Fawr Services Ltd | Professional & scientific | 2014 |
| Derwen Holdings Limited | Financial services | 2023 |
| Derwydd Solutions Ltd | Information & communication | 2024 |
| Deryl DIX Training & Consultancy Ltd | Professional & scientific | 2024 |
| Deshi Spice (Swansea) Ltd | Administrative & support | 2017 |
| Desi Kebabs Ltd | Hospitality | 2024 |
| Desi Spice Birkenshaw Ltd | Hospitality | 2018 |
| Design Partnership Limited | Professional & scientific | 2026 |
| Designorth Limited | Professional & scientific | 2023 |
| DESMONDBROS4 Ltd | Construction | 2019 |
| Destiny Hair Limited | Other services | 2020 |
| Detox Tours Ltd | Administrative & support | 2024 |
| Deutsch Autos Ltd | Wholesale & retail | 2016 |
| Deux Singes Ltd | Administrative & support | 2015 |
| Dev's Lounge Taverns Limited | Hospitality | 2025 |
| Deved Ortho Services Ltd | Health & social care | 2023 |
| Develop Potential Limited | Extraterritorial | 1999 |
| Development Wise Ltd | Construction | 2022 |
| Devois Interiors Limited | Construction | 2014 |
| Devonald Griffiths John Limited | Professional & scientific | 2005 |
| Devonald Hearing Ltd | Wholesale & retail | 2023 |
| Devsecure Limited | Information & communication | 2026 |
| Devysys Limited | Information & communication | 2011 |
| Dewi Development Ltd | Information & communication | 2018 |
| Dewkes Limited | Wholesale & retail | 2020 |
| Dewsbury Court Management Company (Swansea) Limited | Professional & scientific | 1983 |
| Dex-Elec Ltd | Construction | 2019 |
| Dex-Renovations Ltd | Construction | 2023 |
| Dexic Personnel Ltd | Administrative & support | 2022 |
| Dezrez Holdings Limited | Financial services | 2026 |
| Dezrez Services Limited | Information & communication | 1999 |
| Dezrezlegal Limited | Professional & scientific | 2007 |
| DFC Swansea Ltd | Hospitality | 2020 |
| DG Investment Properties Limited | Real estate | 2024 |
| DG Joinery Installations Ltd | Construction | 2019 |
| DGL Accountancy Services Limited | Professional & scientific | 2016 |
| DH Brickwork Services Ltd | Construction | 2023 |
| DH Group Holdings Limited | Financial services | 2023 |
| DH Group Limited | Construction | 2007 |
| DH Taxis (Swansea) Limited | Transport & logistics | 2010 |
| Dh-Pcm Ltd | Professional & scientific | 2024 |
| DHC IT Ltd | Information & communication | 2025 |
| Dhwd Limited | Construction | 2009 |
| Diago Holdings Ltd | Real estate | 2024 |
| Diago Properties Ltd | Real estate | 2021 |
| Diago Property Managment Ltd | Households | 2023 |
| Diago Sports and Social Club Ltd | Hospitality | 2026 |
| Dial Carpentry Ltd | Construction | 2023 |
| Diamond Alloys Swansea Limited | Wholesale & retail | 2020 |
| Diamond Bookings and Management Limited | Arts & recreation | 2017 |
| Diamond Car Wash Swansea Ltd | Administrative & support | 2025 |
| Diamond Properties (Swansea) Limited | Real estate | 2008 |
| Diamond Properties Gorseinon Limited | Other services | 2014 |
| Diamonds UN Limited | Extraterritorial | 2022 |
| Dias World Wide Solutions Ltd | Wholesale & retail | 2018 |
| Diben CYF | Education | 2022 |
| Dickenstar Limited | Extraterritorial | 2001 |
| Digging Deep CIC | Education | 2023 |
| Digi Reach Ltd | Professional & scientific | 2022 |
| Digital Academic Solutions Limited | Information & communication | 2016 |
| Digital Accessibility Training Ltd | Information & communication | 2019 |
| Digital Nation UK Limited | Information & communication | 1997 |
| Digital Nine Five Limited | Other services | 2019 |
| Digital Tiger Ltd | Information & communication | 2018 |
| Digital Visibility Limited | Professional & scientific | 2025 |
| Digitheum Ltd | Financial services | 2021 |
| Digitrol Holdings Limited | Financial services | 2021 |
| Digs Technology Limited | Information & communication | 2003 |
| Dija Holdings Limited | Financial services | 2019 |
| DIL & DIL Ltd | Wholesale & retail | 2024 |
| Dill Enterprise Ltd | Hospitality | 2025 |
| Dillu Convenience Ltd | Wholesale & retail | 2024 |
| Dilly's Chocolates Limited | Manufacturing | 2018 |
| Dilly's Kitchen Ltd | Hospitality | 2011 |
| Dilosh Rental Limited | Wholesale & retail | 2025 |
| Dilys Films Ltd | Information & communication | 2024 |
| DIM Fashion Ltd | Wholesale & retail | 2026 |