The Holmenkollen Line is an 11.4-kilometre-long (7.1 mi) Oslo Metro line which runs between Majorstuen and Nordmarka in Oslo, Norway. Operating as Metro Line 1, it is the route with the fewest passengers and the only one still to have level crossings and short station platforms. The line runs mostly through residential areas of detached houses, and the upper parts of the line principally serve the recreational area of Nordmarka. Holmenkollen Station is located close to Holmenkollen National Arena which hosts international Nordic skiing tournaments. Voksenkollen Station is not far from Oslo Vinterpark (Winter) and the Oslo Sommerpark (Summer).

The Oslo Metro is the rapid transit system of Oslo, Norway, operated by Sporveien T-banen on contract from the transit authority Ruter. The network consists of five lines that all run through the city centre, with a total length of 85 kilometres (53 mi), serving 101 stations of which 17 are underground or indoors. In addition to serving 14 out of the 15 boroughs of Oslo, two lines run to Kolsås and Østerås, in the neighbouring municipality of Bærum. In 2016, the system had an annual ridership of 118 million.