| Il Birri Oy | Hospitality | 2010 |
| Il Operatore Oy | Professional & scientific | 2021 |
| IlNocreatives Oy | Professional & scientific | 2025 |
| Ilari Kuusisto Oy | Transport & logistics | 1996 |
| Ilari Saulo Oy | Other services | 2021 |
| Ilarin ATK-Ratkaisut Oy | Information & communication | 2021 |
| Ilaro Oy | Financial services | 1997 |
| Ilays Af-Soomaali Oy | Information & communication | 2024 |
| Ile Helsinki Oy | Information & communication | 2023 |
| Iledea Oy | Manufacturing | 2015 |
| Ili Oy | Wholesale & retail | 1991 |
| Ilios Foods Oy | Wholesale & retail | 2024 |
| IlisA Beautystudio Oy | Other services | 2023 |
| Ilja Fashion Oy | Wholesale & retail | 2023 |
| Ilkka Aalto-Setälä Holding Oy | Professional & scientific | 2007 |
| Ilkka Kainulainen Oy | Construction | 2002 |
| Ilkka Kikkailee Oy | Professional & scientific | 2026 |
| Ilkka Lundmark Ky | | 1982 |
| Ilkka Olavi Tolonen Oy | Arts & recreation | 2023 |
| Ilkka Pensola Oy | Professional & scientific | 1978 |
| Ilkka Vainio Tuotanto Oy | Manufacturing | 2014 |
| Ilkka-Palvelut Oy | Hospitality | 2019 |
| Ilkkarola In Joy, Ilkan ja Karolan Healing- ja Konsultointiapu avoin yhtiö | Health & social care | 2014 |
| Illankajo MRH Oy | Other services | 2014 |
| Illatsut Oy | Financial services | 1990 |
| Illegal Oy | Information & communication | 2019 |
| Illen kauppa Oy | Wholesale & retail | 2021 |
| Illes Oy | Real estate | 2019 |
| Illevaaran Tuulivoima Oy | Energy | 2013 |
| Illi Apartments Oy | Real estate | 2023 |
| Illume International Oy | Information & communication | 2010 |
| Illume National Oy | Information & communication | 2022 |
| Illume Oy | Information & communication | 1987 |
| Illumina Finland Oy | Professional & scientific | 2017 |
| Illuminus Family Ab | Professional & scientific | 2021 |
| Illuminus Finland Oy Ab | Professional & scientific | 1991 |
| Illusian Capital Oy | Financial services | 2022 |
| Illusian Group Oy | Financial services | 2014 |
| Illusian Holding Oy | Financial services | 2022 |
| Illusian Operations Oy | Administrative & support | 2023 |
| Illusian Oy | Financial services | 2011 |
| Illusian Ventures I GP Oy | Financial services | 2022 |
| Illusian Ventures I HoldCo Oy | Financial services | 2026 |
| Illusian Ventures I Ky | Financial services | 2022 |
| Illusian Ventures II GP Oy | Financial services | 2024 |
| Illusian Ventures II Ky | Financial services | 2024 |
| Illusion Events Oy | Arts & recreation | 2022 |
| Illuusio Suunnittelu Oy | Arts & recreation | 1984 |
| Illuvatar Capital Oy | Financial services | 2019 |
| Ilma Kuru Investments Oy | Professional & scientific | 2024 |
| Ilma Unlimited Oy | Construction | 2022 |
| Ilma-Ahti Oy | Construction | 1994 |
| Ilmakunnas Capital Oy | Financial services | 2020 |
| Ilmakunnas-Engblom Oy | Wholesale & retail | 2020 |
| Ilmala RND Oy | Information & communication | 2015 |
| Ilmala Shops Oy | Wholesale & retail | 2023 |
| Ilmalan Aura HoldCo Ky | Real estate | 2022 |
| Ilmansuunta Oy | Financial services | 1990 |
| Ilmar Watches Oy | Manufacturing | 2015 |
| Ilmari Juhani Oy | Professional & scientific | 2019 |
| Ilmari Tuomi & Co | Transport & logistics | 1962 |
| Ilmarts Oy | Arts & recreation | 2017 |
| Ilmastointi Expertti Oy | Other services | 2020 |
| Ilmastointijokeva Oy | Construction | 2015 |
| Ilmastointimittaus Ari Sara Oy | Professional & scientific | 1989 |
| Ilmastointimittaus Lind Oy | Construction | 2010 |
| Ilmasystem Oy | Wholesale & retail | 2009 |
| Ilmatar Alajärvi Koskenkylä Oy | Energy | 2022 |
| Ilmatar Alajärvi-Louhukangas Oy | Energy | 2013 |
| Ilmatar Alajärvi-Möksy Oy | Energy | 2013 |
| Ilmatar Battery Development Oy | Energy | 2023 |
| Ilmatar Bothnia & Bothnia West Ab | Energy | 2023 |
| Ilmatar Energy HoldCo Oy | Energy | 2018 |
| Ilmatar Energy Oy | Energy | 2023 |
| Ilmatar Haapavesi Oy | Energy | 2023 |
| Ilmatar Hamina Oy | Energy | 2011 |
| Ilmatar Hartola Oy | Energy | 2011 |
| Ilmatar HoldCo Kaksi Oy | Energy | 2022 |
| Ilmatar HoldCo Yksi Oy | Energy | 2021 |
| Ilmatar Honkaselkä Oy | Energy | 2022 |
| Ilmatar Humppila-Urjala Oy | Energy | 2019 |
| Ilmatar Ii Kaksi Oy | Energy | 2021 |
| Ilmatar Ii Oy | Energy | 2011 |
| Ilmatar Ikaalinen-Hämeenkyrö Oy | Energy | 2021 |
| Ilmatar Isokeidas Oy | Energy | 2021 |
| Ilmatar Kajaani Oy | Energy | 2021 |
| Ilmatar Karvia Oy | Energy | 2021 |
| Ilmatar Kauhajoki Oy | Energy | 2021 |
| Ilmatar Kotaselkä Oy | Energy | 2022 |
| Ilmatar Kotka Oy | Energy | 2013 |
| Ilmatar Kristiinankaupunki Kaksi Oy | Energy | 2021 |
| Ilmatar Kristiinankaupunki Oy | Energy | 2012 |
| Ilmatar Kuortane Oy | Energy | 2021 |
| Ilmatar Kurikka Oy | Energy | 2013 |
| Ilmatar Köyliö Oy | Energy | 2020 |
| Ilmatar Laihia Kattiharju Oy | Energy | 2022 |
| Ilmatar Laihia Oy | Energy | 2022 |
| Ilmatar Lapinjärvi Oy | Energy | 2021 |
| Ilmatar Loviisa Oy | Energy | 2012 |
| Ilmatar Lylyharju Oy | Energy | 2018 |