Marka is the name of the forested and hilly areas surrounding Oslo, Norway. It includes areas within the municipality of Oslo, but also large areas in Hole, Ringerike, Jevnaker, Lunner, Nittedal, Bærum, Asker, and other municipalities in Oppland and Akershus counties.

The name is actually just the finite form of mark (Norse mǫrk f) 'woodland, forest'. (See also Marker and Aremark.)

The term Oslomarka is usually used for all the recreational areas around Oslo. Marka is the administrative name for the part of it that lies inside the city limits. Neighboring municipalities (most of which lie in Akershus) do not have the same kind of administrative division as Oslo, and thus do not have any separate administrative arrangement for their parts of the area. The area within Oslo municipality is divided into two parts. Though not designated a borough of Oslo, it is a major recreational area for the population of Oslo, and development in the area is for the most part prohibited.

Despite being used frequently by many citizens of Oslo, especially in weekends, the fauna of marka includes such species as lynx, beaver, Eurasian elk and roe deer.

The population and agricultutal areas of Marka are located mainly in two valleys, Sørkedalen and Maridalen.