| Lekeva Oy | Financial services | 2024 |
| Lepolan Tila avoin yhtiö | Agriculture & fishing | 2019 |
| Leveri X Oy | Hospitality | 2023 |
| Liiketalo Revontie Oy | Real estate | 1987 |
| Lustinn Finland Oy | Administrative & support | 2023 |
| Lvi-asennus J.Ukkola Oy | Construction | 2021 |
| Länsirajan Kuljetus Oy | Transport & logistics | 1993 |
| Lääkäripalvelut Jouni Luokkala Oy | Health & social care | 2015 |
| M&M Lepistö Oy | Transport & logistics | 2015 |
| M.J. Garage Oy | Other services | 2020 |
| M2T Invent Oy | Professional & scientific | 2024 |
| MH Ajoneuvoratkaisut Oy | Wholesale & retail | 2026 |
| MM-Rakennuspalvelu Oy | Construction | 2010 |
| MTPI Oy | Financial services | 2023 |
| MVR S. Annala Ky | Transport & logistics | 2003 |
| MaaIlmasta Oy | Professional & scientific | 2012 |
| Maansiirto N Päkkilä Oy | Construction | 2023 |
| Makujen Kiina Oy | Hospitality | 2016 |
| Mapecca Oy | Real estate | 1995 |
| MarMarShop Oy | Wholesale & retail | 2026 |
| Marian Ravintolat Ky | Real estate | 1988 |
| Marketing & Sales Ruuskanen OY | Professional & scientific | 2021 |
| MatSolutions Oy, Ltd | Health & social care | 2020 |
| Matti Tornberg Oy | Other services | 2024 |
| Mattipatti Oy | Professional & scientific | 2016 |
| MePeVä Oy | Real estate | 2019 |
| Mediation Oy LKV | Real estate | 2020 |
| Menoerien Manta Oy | Financial services | 2024 |
| Mervin Kukka Ky | Wholesale & retail | 2005 |
| Metsäkonehuolto Tarkiainen Oy | Manufacturing | 1990 |
| Minelle Fabrics Oy | Wholesale & retail | 2019 |
| Musa-Vintti Oy | Hospitality | 2016 |
| Muurauspalvelu Isola oy | Construction | 2026 |
| Muutto Service Oy | Transport & logistics | 2025 |
| Myynti & Markkinointi Järvenpää Oy | Real estate | 2007 |
| NILA Medical Oy | Wholesale & retail | 2021 |
| NS Development Oy | Professional & scientific | 2015 |
| Naaatti Oy | Wholesale & retail | 2023 |
| Nakoa Oy | Manufacturing | 2020 |
| Nehvonen Oy | Transport & logistics | 2014 |
| Niskasset Oy | Professional & scientific | 2023 |
| NordenSteel Oy | Professional & scientific | 2011 |
| Nyymanni Oy | Hospitality | 2015 |
| OULUN MAINOSPALVELU Ky | Manufacturing | 2010 |
| Ocotec Oy | Manufacturing | 1991 |
| Oiwa Oy | Wholesale & retail | 2024 |
| Oncamo Oy | Wholesale & retail | 2025 |
| Onkamon Konepaja Oy | Manufacturing | 2023 |
| Onnie Oy | Education | 2023 |
| Osana Invest Oy | Financial services | 2009 |
| Osk Vasako Service | Other services | 2018 |
| Osmon Liikennekoulu Ky | Education | 1994 |
| Osuuskunta Oulun Verso | Professional & scientific | 2006 |
| Oterman's Oy | Construction | 2026 |
| Oulun Datapiste Oy | Wholesale & retail | 1989 |
| Oulun Lasermerkintä Avoin Yhtiö | Manufacturing | 2015 |
| Oulun Mega keittiö Oy | Wholesale & retail | 2003 |
| Oulun Seudun Tele & Audio Oy | Construction | 1994 |
| Oulun huoneistoinvest Oy | Financial services | 1991 |
| Oulun piha & salaoja Sepät Oy | Wholesale & retail | 2011 |
| Oulunseudun Huoltopalvelu Avoin yhtiö | Real estate | 2005 |
| Ouluvision Ky | Construction | 2015 |
| Oy Brånson Ab | Administrative & support | 2020 |
| Oy FF-Chemicals Ab | Manufacturing | 1985 |
| Oy Great Hawk Ab | Wholesale & retail | 1994 |
| P & T Karjalainen Oy | Transport & logistics | 2009 |
| P&H EsVo Group Oy | Other services | 2015 |
| Paikallis-Lämpö Oy | Construction | 2020 |
| Pajasampo Oy | Professional & scientific | 1978 |
| Pajuka Oy | Construction | 2021 |
| Pajuluoto Engineering Oy | Professional & scientific | 2015 |
| Panimo Narri Oy | Manufacturing | 2019 |
| PeMa Kiinteistöt Oy | Real estate | 2013 |
| Peikkohirsi Oy | Manufacturing | 2022 |
| Pelio Oy | Information & communication | 2008 |
| Pelti-Group Oy | Construction | 2022 |
| Peltimylly Oy | Construction | 2019 |
| Peltisepänliike H Kärsämä Ky | Construction | 1990 |
| PinePro Nordic Oy | Construction | 2019 |
| Platinum Group Oy | Professional & scientific | 2024 |
| Pohjois-Pohjanmaan rakennuspalvelu Oy | Construction | 2020 |
| Pohjois-Suomen Ammatti-Isännöinti Oy | Real estate | 2017 |
| Pohjois-Suomen autohuolto Oy | Other services | 2024 |
| Pohjola Sport Ky | Wholesale & retail | 1993 |
| Pohjolan Kanootti Oy | Wholesale & retail | 1983 |
| Polarpinnoitus Oy | Construction | 2020 |
| Pop Mainos Oy | Professional & scientific | 2006 |
| Potential Toimitilat Oy | Real estate | 1978 |
| Powermicco Oy | Wholesale & retail | 2011 |
| Profi Tuote Oy | Wholesale & retail | 2014 |
| Prokkari Oy | Professional & scientific | 2020 |
| Propudas Oy | Information & communication | 1997 |
| Psykassi Oy | Health & social care | 2021 |
| Puolen Suomen Taksi Oy | Transport & logistics | 2018 |
| Putaan Invest Oy | Real estate | 2018 |
| Putaan Katsastus Oy | Professional & scientific | 1998 |
| Putaan Kotitalkkari Oy | Administrative & support | 2012 |
| Putaan Kuljetus Duo Oy | Transport & logistics | 2019 |
| Putaan Pirssi Oy | Transport & logistics | 2018 |
| Putaan Radio Väiski Oy | Wholesale & retail | 1995 |