| Snäckö Invest Ab | Administrative & support | 2008 |
| Snälla Tandfen Ab | Health & social care | 2005 |
| Soder Ab | Professional & scientific | 2016 |
| SolarEq Ab | Other services | 2018 |
| SolarWave Alandia Ab | Energy | 2023 |
| Solbacka Smycken Ab | Manufacturing | 2020 |
| Solel Åland Ab | Construction | 2017 |
| Solen Tours Oy Ab | Administrative & support | 2019 |
| Solidcap Ab | Financial services | 2018 |
| Solpark Åland Ab | Energy | 2019 |
| Solstrand Invest Ab | Real estate | 2004 |
| Soludden Invest Ab | Financial services | 2024 |
| Solvik Stugor Ab | Hospitality | 1996 |
| Specialistläkaren VKAB Ab | Health & social care | 2022 |
| Spellby Ab | Agriculture & fishing | 1977 |
| Spinke's restaurang kb | Hospitality | 1988 |
| Sportkompaniet Ab | Wholesale & retail | 1992 |
| Spraka Kommunikation & Event Ab | Professional & scientific | 2026 |
| Stadsträdgården Holding Ab | Financial services | 2015 |
| Staff-Ax Ab | Administrative & support | 2022 |
| Stekarn Ab | Hospitality | 2017 |
| Stenius & Kalm AB | Other services | 2022 |
| Stig Byman Ab | Financial services | 1989 |
| Storagatan 3 AB | Real estate | 2021 |
| Storeax Ab | Real estate | 2014 |
| Straitrock analys Ab | Financial services | 2001 |
| Strandbaren Åland Ab | Hospitality | 2021 |
| Strike International Öppet bolag | Professional & scientific | 2009 |
| Struktura Design Ab | Real estate | 2021 |
| Stråh Handelsträdgård Ab | Wholesale & retail | 2017 |
| Strömbergs Fisk Ab | Agriculture & fishing | 2026 |
| Studio 11 Hår & Make Up Ab | Other services | 2011 |
| Studio Wickström AB | Professional & scientific | 2023 |
| Studio Ö Aktiebolag | Professional & scientific | 2012 |
| Studio36 Interior & Design Ab | Professional & scientific | 2017 |
| Städsystem i Mariehamn Ab | Administrative & support | 2000 |
| Stångskär Ab | Real estate | 1995 |
| Subsea - Åland Ab | Transport & logistics | 1987 |
| Succedo Invest & Consulting Oy Ab | Information & communication | 2012 |
| Svartasten Ab | Financial services | 2025 |
| Svea Invest Ab | Real estate | 2022 |
| Sviby Aviation Ab | Administrative & support | 2020 |
| Sx2 Productions öppet bolag | Information & communication | 2012 |
| Söderby Solpark Ab | Energy | 2025 |
| Söderlunds Bok & Papper Ab | Wholesale & retail | 1995 |
| Södra Gymmet Ab | Arts & recreation | 2025 |
| Södra Labbholms vattenandelslag | Water & waste | 2018 |
| Södragatan26 Ab | Real estate | 2021 |
| T&M Bokföring Ab | Professional & scientific | 2021 |
| T-Trål Ab | Manufacturing | 1975 |
| TARA Trading Ab | Wholesale & retail | 2005 |
| TAS Konsult Ab | Manufacturing | 2015 |
| TBD Bygg&Entreprenad Oy | Construction | 2026 |
| TCA Svets & Konstruktion Ab | Manufacturing | 2017 |
| TCC Ålclean Ab | Administrative & support | 1997 |
| Tej Invest AB | Construction | 2015 |
| TELMI2 Invest Ab | Professional & scientific | 2024 |
| TEMA rekreation och hälsa AB | Other services | 2010 |
| TJSPC Holding Ab | Financial services | 2025 |
| TLS Fishing & Charter öppet bolag | Arts & recreation | 2017 |
| TM Investments Ab | Other services | 2024 |
| Tranviks Bygg AB | Construction | 2017 |
| TT Åland Ab | Real estate | 2021 |
| Tacticus Ab Ltd | Hospitality | 2022 |
| Tajcum Ab | Professional & scientific | 2008 |
| Takanoha Ab | Information & communication | 2020 |
| Tallum Ab | Real estate | 2021 |
| Tandhygienist Åland Ab | Health & social care | 2015 |
| Tandhygienisten, Kerstin Ekström Ab | Health & social care | 2006 |
| Tandkliniken Pia Holmqvist Ab | Health & social care | 2015 |
| Tank invest Ab | Real estate | 1977 |
| Taste of Himalaya AB | Hospitality | 2025 |
| Taxibolaget 22100 Ab | Transport & logistics | 2017 |
| Taxiservice Åland Ab | Transport & logistics | 2026 |
| Tdl Sofia Sjölund Ab | Financial services | 2021 |
| Teknikpartner Åland Ab | Other services | 1973 |
| Telegrafens Handelshus Ab | Hospitality | 2024 |
| Tenala Buccaneers Ab | Financial services | 2007 |
| Tenala Invest Ab | Financial services | 2007 |
| Terminal Ab Mariehamn | Hospitality | 1975 |
| TextureWave AB | Information & communication | 2022 |
| Thai Orchid i Mariehamn Öppet bolag | Hospitality | 2012 |
| Therese Andersson Media AB | Professional & scientific | 2019 |
| Therina Partner Ab | Professional & scientific | 2024 |
| Tidningstryckarna på Åland Ab | Manufacturing | 1987 |
| Tim Granesäter Ab | Hospitality | 2010 |
| Tindra Productions Ab | Arts & recreation | 2010 |
| Tipitents AB | Hospitality | 2023 |
| To Do Aland Ab | Information & communication | 2021 |
| ToRo Tug Ab | Transport & logistics | 2016 |
| ToRo Tug Holding Ab | Transport & logistics | 2017 |
| Tolk AX Ab | Professional & scientific | 2023 |
| Tom Häggblom Ab | Agriculture & fishing | 2019 |
| Tomsu Invest Ab | Real estate | 2012 |
| Tonik Invest Ab | Wholesale & retail | 2020 |
| Tonårsbutiken Ab | Wholesale & retail | 1974 |
| Trafikskola Spoof Ab | Education | 2019 |
| Transgroup Ab Ltd | Transport & logistics | 2020 |
| Transmar Ab | Transport & logistics | 1960 |
| Trean ab | Real estate | 1972 |