| Telltale AS | Professional & scientific | 2021 |
| TEMA MONTASJE Ellefsen ANS | Wholesale & retail | 1984 |
| Temas Eiendom AS | Real estate | 2009 |
| Temel Holding AS | | 2025 |
| Temper'N AS | Other services | 2021 |
| Tempo Investering AS | Professional & scientific | 2014 |
| Teneka AS | Financial services | 1991 |
| Teppefliser.Com AS | Wholesale & retail | 2014 |
| Terje Fredriksen Holding AS | | 2025 |
| Terra Consult AS | Professional & scientific | 2023 |
| Testall AS | Professional & scientific | 2018 |
| Tfo AS | Professional & scientific | 2017 |
| TG Event AS | Administrative & support | 2012 |
| TG14 Utleie AS | Real estate | 2021 |
| Tgtjenester AS | Manufacturing | 2018 |
| TH Landskap AS | Construction | 2024 |
| Tharaldsen Holding AS | | 2026 |
| The Blue Taj AS | Hospitality | 2024 |
| The North Drum AS | Education | 2017 |
| The Room Bergen AS | Education | 2025 |
| The Room Norge AS | Other services | 2018 |
| The Room Skien AS | Education | 2017 |
| The Skin AS | Health & social care | 2021 |
| Theotek AS | Wholesale & retail | 2025 |
| Thermonatrix AS | Manufacturing | 2010 |
| Thilmas AS | Professional & scientific | 2014 |
| Third Brigade Da | Arts & recreation | 2009 |
| Thole AS | | 2026 |
| Thor Thermo Clothing AS | Wholesale & retail | 2020 |
| Thore Holding AS | Wholesale & retail | 2005 |
| Thoresen Eiendom AS | Real estate | 2005 |
| Thorsen Bygg Og Eiendom AS | Real estate | 2009 |
| Thovsland Invest AS | Transport & logistics | 2013 |
| Thowsen Holding AS | | 2018 |
| Thure Eiendom AS | Real estate | 2014 |
| Thure Holding AS | | 2022 |
| Thure Media AS | Information & communication | 2014 |
| Thure Trykk AS | Manufacturing | 2001 |
| Ti Holding AS | Financial services | 2005 |
| Tiamo Eiendom AS | Real estate | 2021 |
| Tid for Service AS | Other services | 2019 |
| Tidevann AS | Information & communication | 2021 |
| Tiedemanns Dekkskift AS | Other services | 2026 |
| Tilamork AS | Wholesale & retail | 2019 |
| Tilhengerservice Skien AS | Wholesale & retail | 2012 |
| Tilja Eiendom AS | Real estate | 1997 |
| Tilly Holding AS | Administrative & support | 2008 |
| Tilrettelagt Eiendomsutvikling AS | Construction | 2011 |
| Timberinc AS | Real estate | 2021 |
| Timberinc Eiendom AS | Real estate | 2022 |
| Timeless Beauty Skien AS | Health & social care | 2024 |
| Tinholt Bakeri AS | Manufacturing | 1996 |
| Tinholt Bakeri Lietorvet AS | Wholesale & retail | 2023 |
| Tip Top AS | Wholesale & retail | 2019 |
| Tipp Og Vinn Ans | Wholesale & retail | 2002 |
| Tiramisu Holding AS | | 2025 |
| Tirbi Holding AS | | 2025 |
| Tivers Holding AS | Real estate | 2022 |
| TJ Invest AS | Real estate | 2019 |
| TJJ Holding AS | Financial services | 2005 |
| TK Management AS | | 2021 |
| TKG Drift AS | Administrative & support | 2023 |
| TKK Service AS | Wholesale & retail | 2024 |
| TKM Eiendom AS | Real estate | 2018 |
| TL Holding AS | Wholesale & retail | 2005 |
| TL Maskin Og Eiendom AS | Real estate | 2019 |
| TLT Mur Puss & Flis AS | Construction | 2021 |
| TM Norway AS | Manufacturing | 2011 |
| Tme Eiendom AS | Real estate | 2021 |
| TMN Holding AS | Manufacturing | 2019 |
| TN Eiendom Da | Real estate | 2011 |
| TNB Herkules AS | Wholesale & retail | 2007 |
| Tofangsaz AS | Professional & scientific | 2024 |
| Tojuma Invest AS | | 2026 |
| Tollboden Holding AS | Real estate | 2024 |
| Tollefsen Investment AS | | 2020 |
| Tom & Jerry AS | Information & communication | 2025 |
| Tom Bratsberg Holding AS | Manufacturing | 2020 |
| Tom Holland AS | Professional & scientific | 2004 |
| Tom Kittilsen Holding AS | Wholesale & retail | 2023 |
| Tome Holding AS | | 2019 |
| Tommy Rossbach AS | Administrative & support | 2012 |
| Tomojo AS | Administrative & support | 2014 |
| Tomtegata 1 Bolig AS | Real estate | 2020 |
| Tonika Frisør Og Velvære AS | Other services | 2019 |
| Tonull AS | Wholesale & retail | 2022 |
| Top-Sport Norge AS | Wholesale & retail | 2021 |
| Topograf AS | Professional & scientific | 2023 |
| Topp Hesteutstyr Ans | Wholesale & retail | 1999 |
| Tor Eiendom AS | Real estate | 1985 |
| Tor Entreprenør AS | Construction | 2001 |
| Toras Hytte AS | Arts & recreation | 2019 |
| Torbygget AS | Real estate | 2008 |
| Torg GT.15 AS | Real estate | 2014 |
| TORGEIR2020 AS | Real estate | 2021 |
| Torggata 11 AS | Real estate | 2007 |
| Torggata 3 Bolig AS | Real estate | 2026 |
| Torggata 3 Næring AS | Real estate | 2026 |
| Torggata 5 Skien AS | Real estate | 2020 |
| Torggata 6 AS | Real estate | 2017 |