Norðoyatunnilin (The Northern Isles Tunnel) is with 6,300 m the longest tunnel of the Faroe Islands. It connects the town of Leirvík on Eysturoy under the strait Leirvíksfjørður with the city of Klaksvík on Borðoy.
The Norðoyatunnilin is a road tunnel with two lanes and was finished in April 2006. The official opening was on April 19.
The specific plans for a tunnel to connect the island of Eysturoy and the island of Borðoy are not entirely new. In 1988 Landsverkfrøðingurin (the national engineer) carried out a number of seismic investigations in Leirvíksfjørður (the strait between the two islands). A year earlier, an engineer had drawn up an overall plan showing alternative sites for constructing tunnels. Further surveys in 1988 confirmed that the tunnel plans were considered to be economically viable. Fifteen years after the first surveys, work began on boring the tunnel between Eysturoy and Borðoy. The tunnel is 6.3 km long and goes down to a depth of 150 metres below sea level. The maximum gradient is about 6 per cent.