Marker is a municipality in Østfold county, Norway. The administrative centre of the municipality is the village of Ørje. Marker was created as a new municipality on 1 January 1964 following the merger of the two former municipalities of Rødenes and Øymark.
Øymarksjøen is a lake in the municipalities of Aremark and Marker in Østfold county, Norway.
Rødenessjøen is a lake in the municipalities of Aurskog-Høland in Akershus county and Marker in Østfold county, Norway.