Lillestrøm is a municipality located in Akershus county within the traditional district of Romerike, Norway. It serves as an integral part of the Oslo metropolitan area and functions as the administrative center for its namesake town.
The municipality was established on January 1, 2020, following a merger between the former municipalities of Fet, Skedsmo, and Sørum. With a population of 85,757 inhabitants, it currently ranks as the fourth most populated municipality in Viken.