| R. Kjelbotn Invest AS | Financial services | 2012 |
| R.P Holding AS | | 2024 |
| Raavaren AS | Wholesale & retail | 2025 |
| Rai Rai Entertainment AS | Arts & recreation | 1992 |
| Ramsvika Eiendom AS | Real estate | 1999 |
| Rebekka- Og Odd Fellow-Logene Namsos SA | Other services | 2006 |
| Recon Regnskap A/S | Professional & scientific | 1988 |
| Regnskap Midt AS | Professional & scientific | 2014 |
| Reinbakkan Utvikling AS | Real estate | 2021 |
| Reitans Bistro AS | Hospitality | 2023 |
| Reitans Restaurant Og Bar AS | Hospitality | 2022 |
| Rent a Flat AS | Real estate | 1998 |
| Reperio Yam AS | Professional & scientific | 2021 |
| Rett Og Vrangt AS | | 2023 |
| RFS Eiendom AS | Real estate | 2021 |
| RG Bygg Og Rehabilitering AS | Construction | 2022 |
| Riangalleriet SA | Arts & recreation | 2007 |
| RK Bolig AS | Real estate | 2024 |
| RN Prosjekt AS | Real estate | 2022 |
| Robrygga Eiendomsselskap AS | Real estate | 1998 |
| Robrygga Helse AS | Health & social care | 2008 |
| Robrygga Legekontor AS | Health & social care | 2016 |
| Robrygga Øye AS | Health & social care | 2002 |
| Roh Invest AS | Financial services | 2011 |
| Rollaugs Gate 2 AS | Real estate | 2022 |
| Roman Paszkiewicz Neoprbygg AS | Construction | 2024 |
| Rondo Eiendom AS | Real estate | 2017 |
| Roy-Tonny Fjær AS | Wholesale & retail | 2023 |
| RS Byggservice AS | Real estate | 2014 |
| RS Driftsservice AS | Construction | 2021 |
| Ruudimentary AS | Professional & scientific | 2019 |
| Rånes Lydproduksjoner AS | Information & communication | 1995 |
| Rødli Holding AS | | 2025 |
| Røttesmo Invest AS | Real estate | 2019 |
| Røyrvik Næringspark AS | Real estate | 2022 |
| S & P Variénor AS | Real estate | 2020 |
| S4 Eiendom AS | Real estate | 2015 |
| Safedrive AS | Professional & scientific | 2016 |
| Sagbruksvegen 1 AS | Real estate | 2020 |
| Salong 1 AS | Other services | 2019 |
| Salong Torunn AS | Other services | 2024 |
| Salsnes Filter AS | Manufacturing | 1990 |
| Sandgata 11 AS | Real estate | 2022 |
| Sandgata 9 AS | Real estate | 2019 |
| Sandosvegen 2 AS | Real estate | 2025 |
| Sandosvegen 6 AS | Real estate | 2025 |
| Saur Holding AS | Construction | 2021 |
| Schas AS | Construction | 2005 |
| SCL Eiendom AS | Real estate | 2021 |
| SCL Eiendomsutvikling AS | Real estate | 2021 |
| Scornful Da | Arts & recreation | 2008 |
| Seafood Solutions AS | Manufacturing | 2017 |
| Seaweed Innovations AS | | 2021 |
| Selwåg Investments AS | Health & social care | 2021 |
| Sentrum Bilservice Namsos AS | Other services | 2000 |
| Sentrum Boligutleie AS | Real estate | 2021 |
| Service-Gutta AS | Real estate | 2004 |
| Sh-S Holding AS | Construction | 2014 |
| Sign AS | Professional & scientific | 1997 |
| Sihema AS | | 2021 |
| Sikker Skogrydding AS | Agriculture & fishing | 2014 |
| Sirkka-Lisa Holding AS | Professional & scientific | 2020 |
| Sisi Twins AS | | 2007 |
| Siswi AS | Transport & logistics | 2018 |
| Sivavegen 3 AS | Real estate | 2022 |
| Sivavegen 5 AS | Real estate | 2022 |
| Sivavegen AS | Real estate | 2018 |
| Sivilingeniør Robert Williamsen AS | Professional & scientific | 2000 |
| Sjøsiden Holding AS | | 2005 |
| Sjøsikker AS | Education | 2024 |
| Sjøsikker E-Læring AS | Education | 2025 |
| Sjøstål AS | Wholesale & retail | 2021 |
| Sjøtomta AS | Real estate | 2005 |
| SK Byggetjenester AS | Construction | 2025 |
| Skatlandstranda Eiendom AS | Real estate | 2008 |
| Skoglyveien Barnehage AS | Education | 2024 |
| Skogmo Næringsbygg AS | Real estate | 1924 |
| Skogsenergi AS | Agriculture & fishing | 2023 |
| Skrythals AS | Professional & scientific | 2008 |
| Smart-Control AS | Information & communication | 2016 |
| Snabben Namsos AS | Wholesale & retail | 2016 |
| Snippen AS | Real estate | 1983 |
| Sopinn AS | Hospitality | 2025 |
| Sparebankbygg Namsos AS | Real estate | 2005 |
| Spillum Eiendom AS | Real estate | 2008 |
| Spillumstranda AS | Real estate | 2018 |
| Sport 1 Namsos AS | Wholesale & retail | 2012 |
| Sra Innovation AS | Information & communication | 2013 |
| SRT 4 AS | Real estate | 2022 |
| SRT 8 AS | Real estate | 2022 |
| Statskog Børresen AS | Agriculture & fishing | 1909 |
| Statskog Glomma AS | Agriculture & fishing | 1895 |
| Stavsjøvegen Eiendom AS | Real estate | 2016 |
| Steenkariholding AS | | 2021 |
| Stein Aage Skorstad AS | Health & social care | 2006 |
| Stein Borkmo Holding AS | | 2025 |
| Steinkjer Mote AS | Wholesale & retail | 1996 |
| Stills AS | Wholesale & retail | 2025 |
| STN AS | Wholesale & retail | 2024 |
| Storkaia Holding AS | Real estate | 2022 |