| Skrubbedalsveien 7 Tomt AS | Real estate | 2020 |
| Skrubbedalsveien Eiendom AS | Real estate | 2005 |
| Skyland Arendal AS | Arts & recreation | 2020 |
| Skytterbriller.No AS | Wholesale & retail | 2007 |
| Slaattene Holding AS | Other services | 2015 |
| Sleepmed AS | Wholesale & retail | 2014 |
| Slice AS | Administrative & support | 2022 |
| SLK Eiendom AS | Real estate | 2006 |
| Slåttelia Holding AS | Wholesale & retail | 2021 |
| SM Auto AS | Wholesale & retail | 2024 |
| Smart Bilfix AS | Other services | 2021 |
| Smart Davit AS | Wholesale & retail | 2019 |
| Smart Liquid Membrane AS | Manufacturing | 2021 |
| Smartinfra Advisory AS | Professional & scientific | 2025 |
| Smashed AS | Hospitality | 2020 |
| Smedplassen Holding AS | Health & social care | 2022 |
| Smeigedag Høyåsen AS | Other services | 2026 |
| SMJ Eiendom AS | | 2022 |
| Småbruket AS | Hospitality | 2020 |
| Snehvit Familiebarnehage AS | Education | 2023 |
| SNT Invest AS | | 2025 |
| So Anlegg AS | Construction | 1998 |
| So Eiendom AS | Real estate | 2023 |
| So Maskin AS | Administrative & support | 2004 |
| Solbakken Invest AS | Real estate | 2024 |
| Soletjenn Holding AS | | 2026 |
| Solfjell 1 Invest AS | Real estate | 2024 |
| Sollitoppen Gård AS | Health & social care | 2025 |
| Solliveien AS | Real estate | 2019 |
| Solsiden Arendal AS | Hospitality | 2011 |
| Solver AS | Information & communication | 2019 |
| Solåsen Garasjelag SA | Transport & logistics | 1980 |
| Songe Eiendom AS | Real estate | 2016 |
| Songe Gård Ans | Agriculture & fishing | 2001 |
| Songe Mekaniske Verksted AS | Manufacturing | 2009 |
| Sonkon AS | | 2021 |
| Sophienborg Eiendom AS | Real estate | 2017 |
| Sphere Invest AS | | 2024 |
| Spieler AS | Real estate | 2006 |
| Spikkeland Fysioterapi AS | Health & social care | 2024 |
| Spillerne AS | Manufacturing | 2024 |
| Spirebarn AS | Wholesale & retail | 2025 |
| Spiru Design AS | Wholesale & retail | 2021 |
| Sponvika AS | Real estate | 2006 |
| SPORT1 Arendal AS | Wholesale & retail | 2014 |
| Springkleiv Barnehage AS | Education | 2011 |
| St.Ybes AS | Real estate | 2005 |
| Stable AS | Professional & scientific | 2002 |
| Stankus AS | Wholesale & retail | 2024 |
| Star Bilskade Agder AS | Other services | 1993 |
| Stasjon MH AS | Hospitality | 2019 |
| Stavendal Eiendom AS | Real estate | 2011 |
| Stay Tuned Hospitality AS | Professional & scientific | 2012 |
| Stay Tuned Invest AS | Professional & scientific | 2015 |
| Steenhuset Arendal AS | Hospitality | 2018 |
| Stein Venemyr AS | | 2018 |
| Steinodden Eiendom AS | Real estate | 2009 |
| Sten Moe & Co AS | Professional & scientific | 2024 |
| Stephan Spiik AS | Construction | 2014 |
| Stetoskopet Helsetjenester AS | Health & social care | 2022 |
| Stien Invest AS | Real estate | 2006 |
| Stilrent AS | Administrative & support | 2026 |
| Stoa A-R AS | Other services | 2026 |
| Stoa Antirust AS | Other services | 1988 |
| Stoa Apotek AS | Wholesale & retail | 2023 |
| Stoa Autorep AS | Wholesale & retail | 2018 |
| Stoa Bilsenter AS | Wholesale & retail | 2026 |
| Stoa Bygg AS | | 2019 |
| Stoa Eiendom AS | Real estate | 2019 |
| Stoa Handelspark AS | Real estate | 2006 |
| Stoa Helsehus Drift AS | Real estate | 2023 |
| Stoa Helsehus Eiendom AS | Real estate | 2020 |
| Stoa Idrettsmedisin & Opptrening AS | Health & social care | 2014 |
| Stoa Invest AS | Real estate | 1983 |
| Stoa Lagerseksjon AS | Real estate | 2021 |
| Stoa Legekontor AS | Health & social care | 2005 |
| Stoa Maritim AS | Real estate | 1996 |
| Stoa Maskin AS | Wholesale & retail | 2005 |
| Stoa Møbelsenter AS | Wholesale & retail | 1996 |
| Stoa Møbelsenter Eiendom AS | Real estate | 2010 |
| Stoa Tomteutvikling AS | Real estate | 2016 |
| Stoa Transport at AS | Transport & logistics | 2017 |
| Stoa Transport Og Distribusjon AS | Transport & logistics | 2005 |
| Stoa Transport Og Logistikk AS | Transport & logistics | 2017 |
| Stoa Transport Og Spedisjon AS | Transport & logistics | 2009 |
| Stoaveien 11 AS | Real estate | 2021 |
| Stoaveien 11B AS | Real estate | 2025 |
| Stoaveien 12 AS | Real estate | 2005 |
| Stoaveien 13 AS | Real estate | 2021 |
| Stoaveien 16 Invest AS | Real estate | 2017 |
| Stoaveien 3 AS | Real estate | 2016 |
| Stoaveien 7 AS | Real estate | 2004 |
| Stoaveien Utvikling AS | Real estate | 2021 |
| Storbilvasken AS | Real estate | 2005 |
| Stortuen Transport AS | Transport & logistics | 2021 |
| Strai Kjøkken Arendal AS | Wholesale & retail | 1991 |
| Strand Cafe AS | Hospitality | 2005 |
| Strategaia AS | Information & communication | 2021 |
| Strategy Analytics Limited | Professional & scientific | 2008 |
| Streetfood Arendal AS | Hospitality | 2022 |