Bærum is a municipality in the Greater Oslo Region in Norway. It is part of the electoral district and historical county of Viken County. The administrative centre of the municipality is the town of Sandvika. Bærum was established as a municipality on 1 January 1838. A suburb of Oslo, Bærum is located on the west coast of the city.

Bærum has the highest income per capita in Norway and the highest proportion of university-educated individuals. Bærum particularly its eastern neighbourhoods bordering West End Oslo, is one of Norway's priciest and most fashionable residential areas, leading Bærum residents to be frequently stereotyped as snobs in Norwegian popular culture. The municipality has been voted the best Norwegian place to live in considering governance and public services to citizens.

The physical geography of Bærum is dominated by a craggy coastline along the Oslofjord and inland, hilly areas rising to the north and east, where there are large forested areas. The mountain of Kolsås forms a natural center, but the municipality also includes the secluded valley of Lommedalen. Four major rivers flow through the municipality: Lysakerelven, Sandvikselva, Lomma, and Øverlandselva, and there are numerous lakes, both in residential and forested areas. The official municipality flower is Anemone ranunculoides. The geology of Bærum is part of the Oslo Graben and includes Rhomb porphyry at Kolsås.

Since nearly two-thirds of Bærum's area consists of forests, there are rich opportunities for outdoor activities, such as skiing, hiking, and fishing. The forests are considered part of Marka, the forested areas in and around Greater Oslo. Areas within the municipality of Bærum include Bærumsmarka, Vestmarka, and Krokskogen.