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 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.)