Sørum was a municipality in Akershus county, Norway. It is part of the traditional region of Romerike. The administrative centre of the municipality was the village of Sørumsand. Sørum was established as a municipality on 1 January 1838. The municipality of Blaker was merged with Sørum on 1 January 1962.

Lillestrøm is a municipality in Akershus county. It is located in the traditional district of Romerike. With a population of 85,757 inhabitants, it is the fourth most populated municipality in Viken. It was founded on 1 January 2020 as a merger between former municipalities Fet, Skedsmo and Sørum. The administrative centre of the municipality is the town of Lillestrøm. The town of Lillestrøm is a part of the Oslo metropolitan area.