The tunnel of the Fjord of Oslo (Norwegian Oslofjordtunnel) is an underwater road tunnel located under the fjord of Oslo. It connects the commune of Hurum in the county of Buskerud to the county of Akershus on the Eastern side of the fjord.

The tunnel of the Fjord of Oslo east one of the longest underwater tunnels of Scandinavia. It is 7.200 meters long and reached depth a 134 meters below the sea level, with a slope reaching by place 7%. The tunnel was inaugurated by King Harald V the June 29th 2000, providing an easier means consequently to join the east coasts and West of the fjord of Oslo. This tunnel replaces the old vat which connected Drøbak to Storsand.

The tunnel has a way in each direction, as well as an auxiliary traffic lane in the most sloping zone. Speed is limited to 80 km/h and is controlled using automatic radars. The tunnel is partially financed with the receipt of a toll (located east coast of the tunnel).

The idea to build a tunnel was born following the construction project from a new international airport for Norway. Although the town of Gardermoen was selected for the new airport, the project of tunnel remained. The December 13rd 1996, the Norwegian State gave its agreement. Construction began the April 14th 1997. There were thereafter some closings of the tunnel because of unstable geological activities.