| OKT Talotekniikka Group Oy | Professional & scientific | 2024 |
| OKT Talotekniikka Oy | Construction | 2018 |
| OR-Wellness Oy | Wholesale & retail | 2006 |
| OT-Kumi Oy | Manufacturing | 1989 |
| Olix Oy | Manufacturing | 2018 |
| Optimatek Oy | Construction | 2025 |
| Osk Toripata | Hospitality | 2013 |
| Oulu Equitation Oy | Education | 2015 |
| Oulu Solaris | Energy | 2023 |
| Oulun A-Taksi Oy | Transport & logistics | 2015 |
| Oulun Radiopiste, avoin yhtiö | Wholesale & retail | 1987 |
| Oulun Sähkötalo Oy | Construction | 2014 |
| Oulun Talotekniikka Oy | Construction | 2022 |
| Oulun Yrityskaupat Oy | Professional & scientific | 2024 |
| Oulunkaaren Työterveys Oy | Health & social care | 2019 |
| Oy KLE-150 Ab | Financial services | 2025 |
| P&A Trans Oy | Transport & logistics | 1998 |
| PM Ruukki Oy | Manufacturing | 2006 |
| PR-Rakenne Oy | Construction | 2015 |
| PVO-Vesivoima Oy | Energy | 1992 |
| Paavo Jäppinen Ky | Wholesale & retail | 1982 |
| Padel Ii Oy | Arts & recreation | 2022 |
| Papee Oy | Construction | 2024 |
| Pii Technic Oy | Professional & scientific | 2021 |
| Pimeys Oy | Arts & recreation | 2021 |
| Pitokamu Oy | Hospitality | 2018 |
| Pohjois-Suomen Hoivakiinteistöt Oy | Construction | 2009 |
| Pohjois-Suomen Vuokrakone Oy | Administrative & support | 2012 |
| Pohjolan Hiilitase Oy | Real estate | 2022 |
| Pohjolan Muovityö Oy | Manufacturing | 2020 |
| Pohjolan Rakennusvalvonta Oy | Professional & scientific | 2020 |
| Polarfox Oy | Professional & scientific | 2022 |
| Present Group Oy | Professional & scientific | 2021 |
| PuLa Group Oy | Real estate | 2023 |
| Pub Iisakki Oy | Hospitality | 2024 |
| Puhdistuspojat Ky | Administrative & support | 2013 |
| Puodinkosken Sähkö Oy | Energy | 1988 |
| Pyörivä Pyörä Ky | Other services | 2017 |
| R. Paavola Ky | Construction | 2008 |
| RS Organisations Ab | Wholesale & retail | 2022 |
| RaKal Oy | Construction | 2021 |
| Rakennus Takarautio Oy | Construction | 2021 |
| Rakennus-Tomera Oy | Construction | 2008 |
| Rakennusliike Häyrynen Oy | Construction | 1981 |
| Raktell Oy | Construction | 2017 |
| Rasipa Oy | Administrative & support | 2021 |
| Rautjärvi Solaris Oy | Energy | 2023 |
| Rawhide Production Oy | Professional & scientific | 1989 |
| Reliac Oy | Manufacturing | 1978 |
| Rendiment Oy | Financial services | 1990 |
| Rkm-Palvelu Tokola Oy | Construction | 2026 |
| Rotmans Oy | Manufacturing | 2022 |
| Rotsblok Oy | Construction | 2024 |
| Ruskon Konehuolto Oy | Manufacturing | 1994 |
| Rynkynranta Ky | Hospitality | 2008 |
| S&A Kankaala Oy | Other services | 2016 |
| SK Koulutuspalvelut Oy | Education | 2020 |
| SMJ Urakointi Oy | Transport & logistics | 2020 |
| Salera Oy | Construction | 2007 |
| Samin hierontapalvelu Oy | Health & social care | 2024 |
| Sasa group Oy | Financial services | 2022 |
| Savanto's Enterprise Oy | Information & communication | 2021 |
| Scanvall Finland Oy | Manufacturing | 2010 |
| Secondhand Evenna Oy | Wholesale & retail | 2026 |
| Seitenneljä Oy | Professional & scientific | 2019 |
| Sevenaxis Oy | Manufacturing | 1998 |
| Siikalatva Solaris Oy | Energy | 2023 |
| Sisustuspalvelu Miko Böök Oy | Construction | 2011 |
| Skiira Oy | Information & communication | 2016 |
| Spotmizer Oy | Information & communication | 2024 |
| Suomen Aktiiviomistus Oy | Financial services | 2017 |
| Suomen Aktiiviomistus SPAC I Oy | Financial services | 2023 |
| Suomen Erikoispinnoite Oy | Construction | 2012 |
| Suomen autokauppias Oy | Wholesale & retail | 2020 |
| Sähäkki OY | Construction | 2024 |
| Sähköasennus Mäenpää & Leminen Oy | Construction | 2011 |
| TA-Industrial Oy | Manufacturing | 2023 |
| TM Kitchen Oy | Hospitality | 2026 |
| Taidon Tupa Oy | Hospitality | 2024 |
| Talotaitaja Ky | Wholesale & retail | 2012 |
| Team Siurua Ky | Transport & logistics | 2010 |
| Teollisuuskopla Oy | Professional & scientific | 2021 |
| Terapiapalvelu Muutoksen tukena Oy | Health & social care | 2024 |
| Tervasähkö Oy | Construction | 2019 |
| Terä Tekniikka Oy Pertti Kaikkonen | Manufacturing | 1980 |
| Tiiron Raudoituspalvelu Oy | Construction | 2004 |
| Tikkaskodit Oy | Education | 2013 |
| ToTa Invest Oy | Real estate | 2017 |
| Tobek Oy | Financial services | 2021 |
| Tohmajärvi Solaris Oy | Energy | 2023 |
| Tolokun Etelä Oy | Health & social care | 2023 |
| Tolokun Oy | Health & social care | 2020 |
| Training Mikko Niiranen Oy | Arts & recreation | 2015 |
| Trelevant Oy | Professional & scientific | 2008 |
| Truck & Auto Service Ii Oy | Other services | 2015 |
| Tukkikiito Oy | Transport & logistics | 2015 |
| Tukkitomi Oy | Information & communication | 2026 |
| Tulistop Oy | Professional & scientific | 2021 |
| TuningPiste Oy | Other services | 2023 |
| Tunturisijoitus Oy | Financial services | 2024 |