Moss is a town and municipality in the province of Østfold in Viken county in eastern Norway. It borders in the north to Vestby, in the east to Våler and in the south to Råde. To the west, Moss borders Horten (across the fjord).

Moss has a diverse industrial and commercial environment, art galleries, varied fjord and inland nature with Jeløya, Mossemarka and Vansjø. Moss is centrally located on the east side of the Oslo Fjord midway between Oslo and Sweden and has, among other things, a ferry connection across the Oslo Fjord to Horten and Vestfold. In Moss is also Statens Hus with the County Governor and most of the state's other businesses for Østfold. The town is an important trade and service center for its catchment area, which primarily includes Råde and Våler in Viken, formerly in Østfold; and Son in Viken, formerly in Akershus. Politically, the Moss region includes the municipalities of Moss, Råde and Våler. Sometimes Hobøl and Vestby are also included in the area around Moss. Moss has three upper secondary schools, Kirkeparken vgs and Malakoff vgs which are run by Østfold county municipality. Kirkeparken and Moss upper secondary Steinerskole have recently had new premises built for the school.

The basis for the city of Moss is to be found in a combination of good communications and hydropower. Mossefossen in Mosseelva (also called Mossa, original name Morsa) with a waterfall of approx. 25 meters, lay the foundation for a versatile business community with saws and mills. Mossesundet offered a good harbor, despite a long access north of Jeløya. An alternative anchorage was Værlebukta, which is exposed to southerly and westerly winds.