Øyeren is a lake in the Glomma River watershed, southeast of Lillestrøm. It is located within the municipalities of Enebakk, Skedsmo, Fet, and Rælingen in Akershus county and Spydeberg and Trøgstad municipalities in Østfold county.
Lake Øyeren is the ninth largest lake by area in Norway with a surface area of 84.7 square kilometers (32.7 square miles). It is 101 meters (331 feet) above sea level and 76 meters (249 feet) deep.
