The Hitra Tunnel (Norwegian: Hitratunnelen) is an undersea tunnel connecting the island municipality of Hitra to the mainland municipality of Snillfjord in Sør-Trøndelag county, Norway. The tunnel is 5,645 metres (18,520 ft) long and reaches a depth of 264 metres (866 ft) below sea level, making it the deepest tunnel in the world when it was built.
The tunnel begins in Hitra on the island of Jøsnøya, just south of Sandstad. The tunnel then runs under the Trondheimsleia to the island of Hemnskjela in Snillfjord. There is a small bridge connecting Hemnskjela to the mainland.
The tunnel has 3 lanes. Nearly 2,500 cars are hurtling through it every day. Electronics and pumps are handling over 10,000 gallons of water per hour. (Source: Hitra·Frøya Nr. 46, 36. årgang, Tirsdag 21 juni 2011.)
Media gallery 
View of the south end of the tunnel
View of the bridge connecting Hemnskjela to the mainland