| TSV Invest Oy | Financial services | 2019 |
| Tsv-Rakennus OY | Construction | 2010 |
| TT-Group Oy | Financial services | 2018 |
| TTK Service Oy | Transport & logistics | 2022 |
| Tuovie OY | Transport & logistics | 2014 |
| Taalovaara Group Oy | Real estate | 2009 |
| Taida Trading Oy | Professional & scientific | 2013 |
| Takova Group osk | Professional & scientific | 2014 |
| Taksipalvelu Henri Schoultz Ky | Transport & logistics | 2019 |
| Talli Laivakangas Oy | Real estate | 2024 |
| Talli Lapinlumo Oy | Agriculture & fishing | 2023 |
| Tammela Tauno Oy | Professional & scientific | 2016 |
| Tampereen Säästö-Tex Oy | Wholesale & retail | 1986 |
| Tanssikoulu STAGE oy | Education | 2008 |
| Tapojärven Kiinteistöt Oy | Real estate | 1991 |
| Tapojärvi Oy | Mining & quarrying | 1991 |
| Tatun Tarvike Oy | Wholesale & retail | 1978 |
| TeMeCraft Avoin yhtiö | Wholesale & retail | 2014 |
| Team Racing Joki Ky | Arts & recreation | 2001 |
| Tekevä Lappia Osuuskunta | Administrative & support | 2024 |
| Teo-Kupi Oy | Manufacturing | 2010 |
| Teollisuusautomaatiot Markku Autio Oy | Manufacturing | 2009 |
| Terapia-ja Tutkimuspalvelut Neppu Oy | Health & social care | 2019 |
| Terratum Oy | Professional & scientific | 2021 |
| Three Man Stable Oy | Agriculture & fishing | 2012 |
| Tianmar Oy | Wholesale & retail | 2024 |
| Tietomassa Oy | Information & communication | 1992 |
| Tietoverkkopalvelu KuituKuuselat Oy | Construction | 2014 |
| Tiikerihaku Oy | Information & communication | 2026 |
| TikMa Oy | Construction | 2019 |
| Tilausliikenne J. Ylimäki Ky | Transport & logistics | 1997 |
| Tilausliikenne Pekka Jussila Ky | Transport & logistics | 2007 |
| Tilitoimisto Erholtz Oy | Professional & scientific | 1982 |
| Tilitoimisto Isto Oy | Professional & scientific | 2022 |
| Tilitoimisto Kesti Oy | Professional & scientific | 1971 |
| Tilitoimisto Rantala Oy | Professional & scientific | 1981 |
| Tilitoimisto Ravelin Oy | Professional & scientific | 2009 |
| Tilitoimisto Satu Wähä Oy | Professional & scientific | 2023 |
| Tiliylläs Oy | Professional & scientific | 1989 |
| Tilora Oy | Professional & scientific | 2026 |
| Tiltek Oy | Construction | 1987 |
| Timanttikruunu Oy | Health & social care | 2023 |
| Timapuu Oy Marttila | Construction | 2000 |
| Timpan Tori Ky | Wholesale & retail | 1992 |
| TimpuriJussi Oy | Construction | 2006 |
| Tinke Solutions Oy | Financial services | 2016 |
| Tomicus Oy | Manufacturing | 2020 |
| Tonyko Oy | Financial services | 1991 |
| Topi Data Ky | Wholesale & retail | 1994 |
| Toppala Racing Team Ky | Arts & recreation | 2011 |
| Topplattiat Ky | Construction | 2018 |
| TorKK Center Oy | Arts & recreation | 2011 |
| Toranda Oy | Hospitality | 1992 |
| Tormets Oy | Manufacturing | 2012 |
| Tornio City Hotel & Restaurants Oy | Hospitality | 2007 |
| Tornio Golf Oy | Arts & recreation | 2010 |
| Tornio Padel Oy | Arts & recreation | 2025 |
| Tornio Thai Restaurant Oy | Hospitality | 2025 |
| Tornion AlPi Kiinteistöt Oy | Real estate | 2020 |
| Tornion Asennus Oy | Professional & scientific | 1989 |
| Tornion Autoapu Oy | Other services | 2008 |
| Tornion Autokeskus Oy | Wholesale & retail | 1994 |
| Tornion Autotarvike Oy | Wholesale & retail | 2022 |
| Tornion Ekopuu avoin yhtiö | Agriculture & fishing | 2011 |
| Tornion Energia Oy | Energy | 2002 |
| Tornion Erikoislääkärikeskus Oy | Health & social care | 1983 |
| Tornion Foto-Wille Ky | Wholesale & retail | 1986 |
| Tornion Graniitti Oy | Manufacturing | 2019 |
| Tornion Harjateräs Oy | Construction | 2001 |
| Tornion Hitsauspalvelu Oy | Manufacturing | 2022 |
| Tornion Isännöinti Oy | Real estate | 2015 |
| Tornion Kalustekeskus Oy | Administrative & support | 1995 |
| Tornion Kauppa Oy | Wholesale & retail | 1994 |
| Tornion Keilahalli Oy | Arts & recreation | 1985 |
| Tornion Keskusgrilli Oy | Hospitality | 2025 |
| Tornion Kiinteistökolmio Oy | Real estate | 2002 |
| Tornion Kodinkone Oy | Wholesale & retail | 2019 |
| Tornion Kodit Oy | Real estate | 2005 |
| Tornion Konehalli avoin yhtiö | Real estate | 1982 |
| Tornion Konepalvelu Oy | Construction | 2017 |
| Tornion Koneyhtymä Osk | Agriculture & fishing | 2015 |
| Tornion Krunni Oy | Real estate | 1972 |
| Tornion Kukkakeidas Oy | Wholesale & retail | 2016 |
| Tornion Kuntoutus Oy | Health & social care | 1990 |
| Tornion LVI-Palvelu Oy | Construction | 1991 |
| Tornion Laatulattiat Oy | Construction | 1991 |
| Tornion Laki & Talous Oy | Professional & scientific | 1983 |
| Tornion Lasi Oy | Construction | 2019 |
| Tornion Lasihallit Oy | Real estate | 2019 |
| Tornion Laukku ja Käsine Oy | Wholesale & retail | 2016 |
| Tornion Lauttapojat Oy | Construction | 1987 |
| Tornion Lihakarja Oy | Agriculture & fishing | 1997 |
| Tornion Logistiikka Center Oy | Transport & logistics | 2011 |
| Tornion Lohen kyynel-uistin avoin yhtiö | Manufacturing | 1995 |
| Tornion Majoitus ja Tilavuokraus Oy | Hospitality | 2024 |
| Tornion Merityö Oy | Transport & logistics | 2012 |
| Tornion Moottorikoneistamo Oy | Manufacturing | 1981 |
| Tornion Nuohouspalvelu Oy | Administrative & support | 2010 |
| Tornion Olavinlinna Oy | Wholesale & retail | 2016 |
| Tornion Paakarit Oy | Manufacturing | 1992 |