| Aufwin Holding 3 Oy | Financial services | 2016 |
| Aufwin Holding Espanja II Oy | Financial services | 2021 |
| Aufwin Holding Espanja Oy | Financial services | 2017 |
| Aufwin Holding Oy | Financial services | 2017 |
| Aufwin Kiinteistökehitys Espanja II Holding Oy | Financial services | 2022 |
| Aufwin Kiinteistökehitys Espanja II Ky | Financial services | 2020 |
| Aufwin Kiinteistökehitys Espanja III Ky | Financial services | 2023 |
| Aufwin Life Oy | Financial services | 2022 |
| Aufwin Oy | Financial services | 2013 |
| Augmented Reality Vision Ocular - AR.VO AB | Information & communication | 2021 |
| Augmentti Oy | Information & communication | 2026 |
| Augusta Life Sciences Finland Oy | Wholesale & retail | 2025 |
| AugustoLA Oy | Education | 2026 |
| Auliksen Paja Oy | Manufacturing | 2021 |
| Auno Eloranta & Co | Transport & logistics | 1962 |
| Aura Sur Oy | Hospitality | 2025 |
| Aurette Oy | Wholesale & retail | 2025 |
| Aurien Oy | Financial services | 2024 |
| Aurifera Oy | Financial services | 1996 |
| Auriga Group Oy | Administrative & support | 2020 |
| Auriga Oy | Transport & logistics | 2009 |
| Aurinia Oy | Professional & scientific | 2002 |
| Aurinkobussit Oy | Transport & logistics | 1998 |
| Aurinkoinsinöörit Oy | Wholesale & retail | 2009 |
| Aurinkokukka Oy | Hospitality | 2020 |
| Auromatic Oy | Wholesale & retail | 1992 |
| Aurora Borealis Consulting Oy | Professional & scientific | 2012 |
| Aurora CLTrade Oy | Professional & scientific | 2021 |
| Aurora Express Oy | Transport & logistics | 2024 |
| Aurora Linnea Oy | Financial services | 2004 |
| Aurorahoiva Oy | Wholesale & retail | 2025 |
| Aurus oy | Construction | 2026 |
| Austrum Oy | Real estate | 1997 |
| Auto 55 Oy | Wholesale & retail | 2017 |
| Auto Ads Oy | Professional & scientific | 2021 |
| Auto Bassadone Oy | Wholesale & retail | 2014 |
| Auto Fix III Oy | Other services | 2021 |
| Auto Juspek Oy | Wholesale & retail | 2012 |
| Auto MAN Oy | Wholesale & retail | 2015 |
| Auto Prefix Oy | Other services | 2025 |
| Auto Vantaankoski Oy | Other services | 2021 |
| Auto- ja Teollisuusmaalaamo Oy | Other services | 1947 |
| Auto-Ahonen Oy | Other services | 1970 |
| Auto-Artikkeli Oy | Wholesale & retail | 1977 |
| Auto-Avia Oy | Wholesale & retail | 2018 |
| Auto-Bon Ital Oy | Wholesale & retail | 2014 |
| Auto-Bon Oy | Wholesale & retail | 1996 |
| Auto-Finger Oy | Wholesale & retail | 2008 |
| Auto-In Pori Oy | Wholesale & retail | 2013 |
| Auto-Jubil Oy | Other services | 1990 |
| Auto-Lahela Oy | Other services | 1978 |
| Auto-Origo Oy | Wholesale & retail | 1989 |
| Auto-Planet Oy | Wholesale & retail | 2022 |
| AutoAnamaker OY | Other services | 2015 |
| AutoSpa Kasarmintori Oy | Other services | 2022 |
| AutoStep Oy | Transport & logistics | 2009 |
| Autoambulance Group Oy | Transport & logistics | 2022 |
| Autoapu Kauhanen Oy | Other services | 1999 |
| Autoasia Ky | Other services | 2017 |
| Autocare Ky | Other services | 2008 |
| Autodiag Oy | Other services | 2023 |
| Autofix LOKAL oy | Other services | 2022 |
| Autogent Oy | Wholesale & retail | 2022 |
| Autohoitaja Avoin yhtiö | Other services | 2016 |
| Autohuolto Auto-Kulta Oy | Other services | 1996 |
| Autohuolto Avas Oy | Other services | 2020 |
| Autohuolto Liede Oy | Other services | 2008 |
| Autohuolto Väätäinen Oy | Other services | 2010 |
| Autoilija Timo Halonen Oy | Transport & logistics | 2020 |
| Autojenkuljetus SE Mäkinen Oy | Transport & logistics | 1976 |
| Autokaveri Oy | Other services | 2023 |
| Autoklinikka-yhtiöt Oy | Other services | 2009 |
| Autokonttori Oy | Wholesale & retail | 2018 |
| Autokorjaamo Alanko Oy | Other services | 2010 |
| Autokorjaamo K Norring Oy | Other services | 1983 |
| Autokorjaamo Kujala Oy | Other services | 1991 |
| Autokorjaamo Marcos Oy | Other services | 2025 |
| Autokorjaamo Viinikka Oy | Other services | 2008 |
| Autokoulu Martsarin liikenneopisto Oy | Education | 1994 |
| Autokoulu Strada Oy | Education | 1986 |
| Autokoulu Tik-Tak Oy | Education | 2016 |
| Autokoulu Vauhti Oy | Education | 1965 |
| Autola Group Oy | Wholesale & retail | 2007 |
| Autoliike Blacks Oy | Wholesale & retail | 2021 |
| Autolikavex Oy | Other services | 2019 |
| Automaatio I.Herttua Oy | Professional & scientific | 2000 |
| Automaatti-Virtanen Oy | Professional & scientific | 1977 |
| Automatius Oy | Professional & scientific | 2021 |
| Automax Partners Oy | Other services | 2000 |
| Automyynti Carman Oy | Wholesale & retail | 2006 |
| Autopesu Meti Oy | Wholesale & retail | 2015 |
| Autopesu Tapiolapark Oy | Other services | 2025 |
| Autora Oy | Other services | 2024 |
| Autoradioasentamo Nyqvist Oy | Other services | 1989 |
| Autorekry Oy | Administrative & support | 2020 |
| Autosire Oy | Wholesale & retail | 1982 |
| Autospedition Group Oy | Transport & logistics | 2015 |
| Autosta Oy | Other services | 2020 |
| Autotapahtumatehdas Oy | Administrative & support | 2018 |
| Autotek Finland Oy | Wholesale & retail | 2009 |