| Sifi AS | Real estate | 1996 |
| Sigerfjord Dekk & Service AS | Other services | 2024 |
| Sigerfjord Eiendom AS | Real estate | 2010 |
| Sigerfjord Fisk AS | Manufacturing | 1992 |
| Sigerfjord Innovasjon Eiendom AS | Real estate | 2012 |
| Sigerfjord Marine Innovasjonssenter AS | Professional & scientific | 2023 |
| Sigerfjord Produksjon AS | Manufacturing | 2023 |
| Sigerfjord Samfunnshus SA | Real estate | 1965 |
| Sigerfjord Sand AS | Mining & quarrying | 1993 |
| Sigerfjord Settefisk AS | Agriculture & fishing | 2024 |
| Sigerfjordbygg AS | Construction | 2020 |
| Sikker Trafikkopplæring Vesterålen AS | Education | 2007 |
| Sikker Transport AS | Education | 2012 |
| Sikker.No AS | Wholesale & retail | 1995 |
| Sildpollen Og Lahaugen Skogsveilag SA | Construction | 2009 |
| Sivilingeniør Gøran Skogvoll AS | Professional & scientific | 2025 |
| Sjkgf Invest AS | | 2026 |
| Sjøhaugen Gårdsdrift Da | Agriculture & fishing | 2026 |
| Sjøsiden Eiendom AS | Real estate | 2003 |
| Sjøtomta Sortland AS | Real estate | 2021 |
| Skeidar Sortland AS | Wholesale & retail | 2004 |
| Skibsgården AS | Real estate | 1992 |
| Skibsgården Leker AS | Wholesale & retail | 2018 |
| Skipnes Event AS | Arts & recreation | 2018 |
| Skipsaksjeselskapet Taurus | Transport & logistics | 1984 |
| Skjellfjorden Kai AS | Transport & logistics | 2005 |
| Skodda AS | Arts & recreation | 2018 |
| Skogly Eiendom Da | Real estate | 2002 |
| Skogsbilveglaget Reinbergveien SA | Real estate | 1980 |
| Skogsvegen Hornet-Bjørndalen SA | Agriculture & fishing | 1992 |
| Slettegaard AS | | 2025 |
| SM Pedersen AS | Professional & scientific | 2026 |
| Smartbiz AS | Education | 2021 |
| Snarsetfisk AS | Agriculture & fishing | 2012 |
| Snekkarlaget AS | Construction | 2001 |
| Snølaks AS | Wholesale & retail | 2025 |
| Soand AS | | 2021 |
| SOAND2 AS | | 2025 |
| Sol Capital AS | | 2026 |
| Sol-Run Invest AS | | 2010 |
| Solbakken Strand AS | Transport & logistics | 2016 |
| Solhjørnet Eiendom AS | Real estate | 1997 |
| Sollie Eiendom AS | Real estate | 2024 |
| Sollie Invest AS | Real estate | 2011 |
| Sommerseth Utleie AS | Real estate | 2019 |
| Sortland Arbeidssenter AS | Health & social care | 1990 |
| Sortland Auto AS | Wholesale & retail | 1995 |
| Sortland Barnefysioterapi AS | Health & social care | 2022 |
| Sortland Beitelag SA | Agriculture & fishing | 1994 |
| Sortland Bil AS | Other services | 2007 |
| Sortland Bilsenter AS | Real estate | 2016 |
| Sortland Blomster AS | Wholesale & retail | 2002 |
| Sortland Bobilutleie AS | Administrative & support | 2026 |
| Sortland Bruktbilutleie AS | Administrative & support | 2020 |
| Sortland Byparkering AS | Transport & logistics | 2024 |
| Sortland Byutvikling AS | Professional & scientific | 2022 |
| Sortland Camping Og Motell AS | Hospitality | 1988 |
| Sortland Caravan AS | Wholesale & retail | 1984 |
| Sortland Caravan Eiendom AS | Real estate | 2009 |
| Sortland Dagligvarer AS | Wholesale & retail | 2020 |
| Sortland Drosjesentral AS | Transport & logistics | 2004 |
| Sortland Eiendom AS | Real estate | 2023 |
| Sortland Elektro AS | Wholesale & retail | 1982 |
| Sortland Elektro Eiendom AS | Real estate | 1961 |
| Sortland Elektro Teknikk AS | Construction | 2001 |
| Sortland Entreprenør AS | Construction | 1988 |
| Sortland Flis AS | Wholesale & retail | 2006 |
| Sortland Fysioterapi Og Manuell Terapi AS | Health & social care | 1985 |
| Sortland Gård AS | Real estate | 2017 |
| Sortland Hotell AS | Hospitality | 2004 |
| Sortland Hud Og Fotterapi AS | Health & social care | 1998 |
| Sortland Idretts Og Fritidspark AS | Real estate | 2000 |
| Sortland Logopedi AS | Health & social care | 2025 |
| Sortland Løypemaskin AS | Arts & recreation | 2008 |
| Sortland Manuellterapi AS | Health & social care | 2020 |
| Sortland Maskin AS | Wholesale & retail | 1985 |
| Sortland Maskin Holding AS | Manufacturing | 2012 |
| Sortland Mat & Vinhus AS | Hospitality | 2014 |
| Sortland Panorama AS | Real estate | 2021 |
| Sortland Sentrumseiendom AS | Real estate | 2024 |
| Sortland Skipselektronikk AS | Professional & scientific | 2003 |
| Sortland Tak&Membran AS | Construction | 2023 |
| Sortland Trafikkskole AS | Education | 2022 |
| Sortland Vaktmester Service Da | Administrative & support | 1994 |
| Sortlandhotellene AS | Hospitality | 1999 |
| Sport 1 Sortland AS | Wholesale & retail | 2003 |
| Stall Rødli AS | Real estate | 2020 |
| Stavøy Eiendom AS | Real estate | 2005 |
| Stavøy Holding AS | Wholesale & retail | 2005 |
| Steimar AS | Administrative & support | 2022 |
| Steinarson AS | Professional & scientific | 2005 |
| Steinbruddet Boliger AS | Real estate | 2023 |
| Steinbruddet Eiendom AS | Real estate | 2010 |
| Steinbruddet Invest AS | Construction | 2018 |
| Steiro Glass AS | Wholesale & retail | 2004 |
| Steiro Hanssen AS | Wholesale & retail | 2004 |
| Steiro Husflid AS | Wholesale & retail | 2013 |
| Steiro Interiør Og Farge AS | Wholesale & retail | 2004 |
| Steiro Invest AS | Real estate | 1998 |
| Steiro Leker AS | Wholesale & retail | 2004 |