| Reiseliv.No AS | Information & communication | 1997 |
| Rekani Bilpleie AS | Other services | 2019 |
| Rekdals Omsorg AS | Health & social care | 2020 |
| Relasjonspartner AS | Information & communication | 2011 |
| Remmen Eiendom AS | Real estate | 2026 |
| Renvix AS | Administrative & support | 2026 |
| Reprocenter AS | Manufacturing | 1973 |
| Restaurant Chinahuset AS | Hospitality | 2002 |
| Restaurant Mother India Sarpsborg AS | Hospitality | 2023 |
| Reton AS | Construction | 2004 |
| Revisor Bjørn a Halle AS | Professional & scientific | 2005 |
| Rhubinoux Holding AS | | 2022 |
| Rib Østfold AS | Administrative & support | 2017 |
| Riddle AS | Arts & recreation | 2019 |
| Rikkes Beauty AS | Other services | 2024 |
| Ringsrød Holding AS | | 2025 |
| Riss + AS | Professional & scientific | 2020 |
| Riss+ Invest AS | Real estate | 2021 |
| RJ Anlegg AS | Construction | 2021 |
| RK Maling Og Event AS | Arts & recreation | 2018 |
| RKS Holding AS | Wholesale & retail | 2005 |
| Ro Catering Og Eventer AS | Hospitality | 2025 |
| Roald Amundsensgt 3 AS | Real estate | 2012 |
| Roald Grasto AS | | 2024 |
| Roar Hagen Consulting AS | Professional & scientific | 2011 |
| Rockworld Publishing AS | Information & communication | 2015 |
| Rolgenor AS | Hospitality | 2012 |
| Rolvsøy Bygg AS | Construction | 2010 |
| Rwi AS | Real estate | 2018 |
| Ryggeveien 33 AS | Real estate | 2005 |
| Ryjat Holding AS | Financial services | 2005 |
| Ryma Invest AS | Real estate | 1983 |
| Råkil Eiendom AS | Construction | 2013 |
| Råkilveien 1 AS | Real estate | 1995 |
| Råkilveien 1 Holding AS | Real estate | 2015 |
| Råslatta Stålhantering AB | Construction | 1999 |
| Rør Øst AS | Construction | 2011 |
| Røret Sveis AS | Construction | 2023 |
| Rørhjelpen AS | Construction | 2015 |
| S B Eiendomsutvikling AS | Real estate | 2017 |
| S B Holding AS | Professional & scientific | 2021 |
| S Bekken Transport AS | Transport & logistics | 1997 |
| S P S Shipping Partner Sarpsborg AS | Transport & logistics | 1986 |
| S. Gangestad Optikk Storbyen AS | Wholesale & retail | 1999 |
| S.B.A Holding AS | | 2023 |
| Saakk AS | Wholesale & retail | 2021 |
| Safir Gullsmedforretning Borg AS | Wholesale & retail | 2008 |
| Saga Legesenter Da | Health & social care | 2011 |
| Saga Mote Ans | Wholesale & retail | 1989 |
| Sah Klinikken AS | Health & social care | 2023 |
| Saha Invest AS | Real estate | 2017 |
| Salbec Holding AS | Real estate | 2023 |
| Salbec Utvikling AS | Real estate | 2025 |
| Salgspartner Østfold AS | Professional & scientific | 2018 |
| Salming Norge AS | Wholesale & retail | 2012 |
| Salong 64 AS | Other services | 2016 |
| Salvesen Cosmetica AS | Other services | 2026 |
| Sam Capital AS | Financial services | 2007 |
| Samsam AS | Information & communication | 2021 |
| Samtak AS | Health & social care | 2019 |
| Sandesund Bilpleie AS | Other services | 2024 |
| Sandh AS | Professional & scientific | 2023 |
| Sandh Holding AS | Professional & scientific | 2023 |
| Sandman AS | | 2021 |
| Sans AS | Administrative & support | 2024 |
| Saren Energy Sarpsborg AS | Energy | 2014 |
| Sarpen Bilpleie AS | Other services | 2020 |
| Sarpen Dagligvare AS | Real estate | 2023 |
| Sarpen Dagligvarer AS | Wholesale & retail | 2020 |
| Sarpen Studios AS | Real estate | 2016 |
| Sarpsborg Arbeiderblad AS | Information & communication | 1997 |
| Sarpsborg Arena AS | Real estate | 1997 |
| Sarpsborg Asvo AS | Health & social care | 1992 |
| Sarpsborg Auto AS | Wholesale & retail | 2026 |
| Sarpsborg Autoservice AS | Other services | 2015 |
| Sarpsborg Bardrift AS | Hospitality | 2025 |
| Sarpsborg Bilverksted AS | Other services | 2015 |
| Sarpsborg Bowlingsenter AS | Arts & recreation | 1989 |
| Sarpsborg Båtutstyr AS | Wholesale & retail | 2013 |
| Sarpsborg Campino Pizzeria AS | Hospitality | 1997 |
| Sarpsborg Data AS | Information & communication | 2014 |
| Sarpsborg Dental AS | Manufacturing | 2016 |
| Sarpsborg Eiendom AS | Real estate | 2013 |
| Sarpsborg Elinstallasjon AS | Construction | 1999 |
| Sarpsborg Flyttebyrå AS | Transport & logistics | 2019 |
| Sarpsborg Fotballklubb Eiendom AS | Real estate | 1992 |
| Sarpsborg Fysioterapi Da | Health & social care | 2020 |
| Sarpsborg Garn & Broderi AS | Wholesale & retail | 2015 |
| Sarpsborg Garn AS | Wholesale & retail | 2023 |
| Sarpsborg Hifi AS | Wholesale & retail | 2024 |
| Sarpsborg Mynthandel AS | Wholesale & retail | 1997 |
| Sarpsborg Naprapatklinikk Og Eiendom AS | Real estate | 2013 |
| Sarpsborg Papp AS | Manufacturing | 1990 |
| Sarpsborg Pizza & Thai Food AS | Hospitality | 2026 |
| Sarpsborg Smådyrklinikk AS | Professional & scientific | 2020 |
| Sarpsborg Spedisjon AS | Transport & logistics | 1989 |
| Sarpsborg Spesialistsenter Eiendom AS | Real estate | 2014 |
| Sarpsborg Telecom AS | Information & communication | 2011 |
| Sarpsborg Trafikkskole AS | Education | 2005 |
| Sarpsborg Trening Og Helse AS | | 2021 |