| Russevikveien 4 AS | Real estate | 2015 |
| Rådhusveien 11 AS | Real estate | 2008 |
| Rødskjær 1 AS | | 2024 |
| Rødskjær Havn Og Næringspark AS | Real estate | 2025 |
| Rødskjær Holding AS | | 2024 |
| Rødskjær Utvikling AS | | 2025 |
| Røkenes Gård & Gjestehus AS | Hospitality | 2013 |
| Røkenes Gård AS | Real estate | 2003 |
| Røsberg Transport AS | Transport & logistics | 1998 |
| S.B-N Invest AS | | 2026 |
| S.Mikkelsen AS | | 2025 |
| S.T.R. Holding AS | Real estate | 2016 |
| S/Y Libra Da | Transport & logistics | 2010 |
| S4 Drift AS | Wholesale & retail | 2021 |
| S4 Holding AS | Wholesale & retail | 2016 |
| Saa A&E AS | Real estate | 2018 |
| Saa Investeringer AS | Real estate | 2015 |
| Sabrinas AS | Other services | 2012 |
| Sabrura Harstad AS | Hospitality | 2022 |
| Sakfører Birger Karluf Eiendom AS | Real estate | 2013 |
| Sakshaug Sport Kanebogen AS | Wholesale & retail | 2021 |
| Salberg Kjøreskole AS | Education | 1997 |
| Salimi Eiendom AS | Real estate | 2022 |
| Saltdalsbygg Nord AS | Construction | 2011 |
| Salten AS | Real estate | 2012 |
| Saltsjøen Invest AS | | 2022 |
| Sama Bygg AS | Real estate | 2024 |
| Samasenteret AS | Real estate | 1993 |
| Sandsøy Aktivitet AS | Arts & recreation | 2018 |
| Sandsøy Eiendom AS | Real estate | 2016 |
| Sandvik Bygg Harstad AS | Construction | 2014 |
| Sani Invest AS | Financial services | 2005 |
| Sarkani Eiendom AS | Real estate | 2017 |
| Sarkani Holding AS | Real estate | 2016 |
| Sarnette AS | Real estate | 1990 |
| Sars Eiendom AS | Real estate | 2007 |
| Satellitt Studio AS | Information & communication | 2020 |
| Saue Eiendom AS | Real estate | 2021 |
| Saxolågen AS | Other services | 2004 |
| SBT Service AS | Hospitality | 2012 |
| Scale Protection AS | Professional & scientific | 2016 |
| Scan Holding AS | Real estate | 2000 |
| Scandinavian Industries Holding AS | Construction | 2021 |
| Scanmark Eiendom AS | Real estate | 2020 |
| Scanmark Norge AS | Manufacturing | 1977 |
| Sea Eco AS | Professional & scientific | 1996 |
| Sea Eco Eiendom AS | Real estate | 2022 |
| Seabyte AS | Information & communication | 2025 |
| Sealinks AS | Professional & scientific | 2026 |
| Seashore Technology AS | Professional & scientific | 2004 |
| Seaworks AS | Transport & logistics | 1995 |
| Seaworks Kabel AS | Construction | 2015 |
| Seaworks Management AS | Transport & logistics | 2010 |
| Sebastian Conrad Fysioterapi AS | Health & social care | 2026 |
| Sebcon Holding AS | | 2026 |
| Securinord AS | Wholesale & retail | 2020 |
| See Nord AS | Professional & scientific | 1997 |
| Segla AS | Real estate | 2024 |
| Selfjord AS | Financial services | 2015 |
| Seljestad Eiendom AS | Real estate | 2016 |
| Seljestad Utvikling AS | Real estate | 2016 |
| Seljestadveien 28 AS | Real estate | 2020 |
| Seljestadveien 48 AS | Real estate | 2005 |
| Seljestadveien 69 AS | Real estate | 2024 |
| Selsbane Holding AS | Real estate | 2019 |
| Selvledelse AS | Education | 2024 |
| Seneca AS | Professional & scientific | 2014 |
| Sennit AS | Construction | 2022 |
| Sentrumsselskapet AS | Administrative & support | 2020 |
| Sep Engineering AS | Professional & scientific | 2024 |
| Servicenord Engros AS | Wholesale & retail | 1986 |
| Shangrila Restaurant AS | Hospitality | 2007 |
| Si Motor AS | Manufacturing | 2014 |
| Sir Alex Holding Harstad AS | | 2021 |
| Sivilingeniør Vang AS | Professional & scientific | 2012 |
| Siviløkonom Ola Karlsen AS | Professional & scientific | 1991 |
| Siwe Elektro AS | Construction | 1981 |
| Siwe Holding AS | Construction | 2014 |
| SJ Dykk AS | Transport & logistics | 2013 |
| SJ Dykk Eiendom AS | Real estate | 2013 |
| SJ Dykk Holding AS | Transport & logistics | 2013 |
| Sjelero I Havgapet AS | Health & social care | 2023 |
| Sjelero I Havgapet Eiendom AS | Real estate | 2025 |
| Sjækerhatten AS | Financial services | 2005 |
| Sjødrift Nord AS | Agriculture & fishing | 2014 |
| Sjøgata 5 AS | Real estate | 2007 |
| Sjøgrunn AS | Real estate | 1996 |
| Sjøkanten Legesenter AS | Health & social care | 2010 |
| Skadeservice Nor 1 AS | Administrative & support | 2022 |
| Skagevold Invest AS | Financial services | 2017 |
| Skansen Eiendom AS | Real estate | 1998 |
| Skarding AS | | 2023 |
| Skeidar Harstad AS | Wholesale & retail | 2004 |
| Skjærveien 10 AS | Real estate | 2025 |
| Sko-Dilla AS | Wholesale & retail | 2026 |
| Skogan Holding AS | Manufacturing | 2024 |
| Skohuset Harstad AS | Wholesale & retail | 1987 |
| Skolegata Eiendom AS | Real estate | 1988 |
| Skrolsen AS | Real estate | 2018 |
| Skymark Holding AS | | 2025 |