| 3FS Services Limited | Professional & scientific | 2019 |
| 3G Capital Investments Ltd | Financial services | 2021 |
| 3G Solutions Limited | Wholesale & retail | 2019 |
| 3G Travels Ltd | Administrative & support | 2017 |
| 3GAAPS Ltd | Professional & scientific | 2021 |
| 3GC Limited | Real estate | 2025 |
| 3GINIS Ltd | Real estate | 2023 |
| 3GLOBAL TOU Ltd | Professional & scientific | 2026 |
| 3GLOBAL Tours Ltd | Wholesale & retail | 2025 |
| 3GM Properties Ltd | Real estate | 2021 |
| 3GO Smiles Limited | Health & social care | 2023 |
| 3GROUP Feste LLP | | 2023 |
| 3GS in UK Limited | Other services | 2011 |
| 3GS Luxury Property Ltd | Real estate | 2024 |
| 3H Beauty Ltd | Other services | 2025 |
| 3H Family Ltd | Wholesale & retail | 2025 |
| 3H Foundry Limited | Administrative & support | 2025 |
| 3H Freehold Limited | Professional & scientific | 2002 |
| 3H Nail Ltd | Other services | 2024 |
| 3H Private Capital Limited | Financial services | 2026 |
| 3H Property Limited | Real estate | 2014 |
| 3H Saigon Ltd | Hospitality | 2026 |
| 3H Site Protection (UK) Ltd | Administrative & support | 2019 |
| 3H&CO Ltd | Wholesale & retail | 2024 |
| 3H20 Capital Ltd | Financial services | 2003 |
| 3H2O Ltd | Professional & scientific | 2025 |
| 3HG Services Ltd | Administrative & support | 2025 |
| 3HIRTY6IX Ltd | Administrative & support | 2019 |
| 3HLIFE Ltd | Wholesale & retail | 2023 |
| 3HLINEN Ltd | Wholesale & retail | 2024 |
| 3HN Homes Limited | Financial services | 2021 |
| 3HN Limited | Professional & scientific | 2013 |
| 3HNDRDS Ltd | Arts & recreation | 2024 |
| 3HOLDS Investment Limited | Real estate | 2015 |
| 3HOLDS Management Limited | Extraterritorial | 2015 |
| 3HORIZONS Ltd | Information & communication | 2022 |
| 3HPP Freehold Limited | Households | 2008 |
| 3HPR Ltd | Households | 2019 |
| 3HREE 2WO Creative Ltd | Professional & scientific | 2022 |
| 3HTS Properties Ltd | Real estate | 2025 |
| 3HY Limited | Wholesale & retail | 2026 |
| 3I 2023 Co-Investment LP | | 2023 |
| 3I 2024 Sapphire LP | | 2025 |
| 3I Amalthea Topco Limited | Financial services | 2021 |
| 3I Asia Pacific 2004-06 LP | | 2004 |
| 3I Asia Pacific Technology LP | | 2000 |
| 3I Aura GP (2022) Limited | Financial services | 2022 |
| 3I Aura L.P. | | 2022 |
| 3I Buyouts 08-10A LP | | 2007 |
| 3I Buyouts 08-10B LP | | 2007 |
| 3I Buyouts 08-10C LP | | 2007 |
| 3I Buyouts 2010A LP | | 2010 |
| 3I Buyouts 2010B LP | | 2010 |
| 3I Buyouts 2010C LP | | 2010 |
| 3I Constructions Ltd | Households | 2021 |
| 3I Digital Limited | Information & communication | 2014 |
| 3I DM GIF 2015 LP | | 2015 |
| 3I EFV GP Limited | Financial services | 2006 |
| 3I EFV Nominees a Limited | Financial services | 2006 |
| 3I EFV Nominees B Limited | Financial services | 2006 |
| 3I Emmi Co-Investment L.P. | | 2024 |
| 3I Europartners II LP | | 1997 |
| 3I Europartners Iiia LP | | 1999 |
| 3I Europartners Iiib LP | | 1999 |
| 3I Europartners IVA LP | | 2002 |
| 3I Europartners IVB LP | | 2002 |
| 3I Europartners IVC LP | | 2004 |
| 3I Europartners IVD LP | | 2003 |
| 3I Europartners IVK LP | | 2004 |
| 3I Europartners VA LP | | 2006 |
| 3I Europartners VB LP | | 2006 |
| 3I Europe PLC | Financial services | 1993 |
| 3I European Mid-Market Infrastructure a L.P. | | 2024 |
| 3I European Mid-Market Infrastructure B L.P. | | 2024 |
| 3I European Mid-Market Infrastructure GP (2024) Limited | Financial services | 2024 |
| 3I European Operational Projects LP | | 2016 |
| 3I GC GP Limited | Financial services | 2009 |
| 3I GC Nominees a Limited | Financial services | 2010 |
| 3I GC Nominees B Limited | Financial services | 2010 |
| 3I GP 2010 Limited | Financial services | 2010 |
| 3I GP 2013 Ltd | Financial services | 2013 |
| 3I GP 2016 Limited | Financial services | 2016 |
| 3I GP 2019 Limited | Financial services | 2019 |
| 3I GP 2022 Limited | Financial services | 2022 |
| 3I Group Investments LP | | 1999 |
| 3I Group PLC | Financial services | 1973 |
| 3I Growth (Asia) 08-10 LP | | 2008 |
| 3I Growth (Europe) 08-10 LP | | 2008 |
| 3I Growth (Og&P) 08-10 LP | | 2008 |
| 3I Growth (USA) 08-10 LP | | 2008 |
| 3I Growth 08-10 LP | | 2007 |
| 3I Growth 2010 LP | | 2010 |
| 3I Growth Capital a LP | | 2010 |
| 3I Growth Capital B LP | | 2010 |
| 3I Growth Capital C LP | | 2010 |
| 3I Growth Capital C-Us LP | | 2010 |
| 3I Growth Capital G LP | | 2010 |
| 3I Growth Capital H LP | | 2010 |
| 3I Holdings PLC | Professional & scientific | 1991 |
| 3I IIF GP 2020 Limited | Financial services | 2020 |