Fet is a municipality in Akershus county, Norway. It is part of the Romerike traditional region. The administrative centre of the municipality is the village of Fetsund.Fet was established as a municipality on 1 January 1838 (see formannskapsdistrikt). The new municipality of Rælingen was separated from Fet on 1 July 1929.The name (Old Norse: Fit) is first recorded in 1321 ("a Fit"). It is the word fit which means "vigorous meadow".
The coat-of-arms is from modern times. They were granted on 19 December 1986. The arms show a logging hook, which in the area was used to haul the logs, cut in the surrounding forests. The logs were transported over the streams and lakes to the sawmills. The people use long poles with hooks to haul the logs. The colours of the arms are green and silver, because the name is derived from an old word describing a field (green) near a lake (silver).