The Oslo Tunnel is a 3,632-metre (2.257 mi), double-track, railway tunnel which runs between Olav Kyrres plass and Oslo Central Station (Oslo S) in Oslo, Norway. The tunnel constitutes the easternmost section of the Drammen Line and runs below the central business district of Oslo. It features the four-track Nationaltheatret Station, Norway's second-busiest railway station, where the Oslo Tunnels lies directly beneath the Common Tunnel of the Oslo Metro. At Frogner, the Elisenberg Station was built, but has never been used. The tunnel is the busiest section of railway line in Norway and serves all west-bound trains from Oslo, including many services of the Oslo Commuter Rail and the Airport Express Train.

The Airport Express Train is a Norwegian high-speed airport railway service connecting Oslo Airport to Oslo Central Station in nineteen minutes. Run by Flytoget AS, it operates on the high-speed Gardermoen Line using sixteen GMB Class 71 electric trains. Normal service frequency is once every ten minutes, with five of the services each hour continuing westwards beyond Oslo Central. The extended services serve nine stops within Greater Oslo and take up to 60 minutes.