As of 2026-04-29, Tur‘at al Khadrāwīyah tops the list with 350 km.
- #1 Tur‘at al Khadrāwīyah — 350 km source Wikidata
- #2 Ar Rayyāḩ at Tawfīqī — 163 km
canal
source Wikidata - #3 Taiwan Strait Tunnel — 150 km
planned undersea rail tunnel
The Taiwan Strait Tunnel Project is a proposed undersea tunnel to connect Pingtan in Mainland China to Hsinchu in Taiwan as part of the G3 Beijing–Taipei Expressway. It has seen a few academic studies from the China side, but no interest from the Taiwan side, which views such proposals as propaganda. In addition to political factors, the project is generally not considered realistic due to technical and cost concerns. Read more on Wikipedia.
Wikidata - #4 Japan–Korea Undersea Tunnel — 150 km
a proposed tunnel connecting Japan and Korea
The Japan–Korea Undersea Tunnel, also known as the Korea–Japan Undersea Tunnel, is a proposed tunnel project to connect Japan with South Korea via an undersea tunnel crossing the Korea Strait that would use the strait islands of Iki and Tsushima, a straight-line distance of approximately 128 kilometers (80 mi) at its shortest. Read more on Wikipedia.
Wikidata - #5 Delaware Aqueduct — 137 km
aqueduct in New York State, U.S.
The Delaware Aqueduct is an aqueduct in the New York City water supply system. It takes water from the Rondout, Cannonsville, Neversink, and Pepacton reservoirs on the west bank of the Hudson River through the Chelsea Pump Station near Beacon, New York, then into the West Branch, Kensico, and Hillview reservoirs on the east bank, ending at Hillview in Yonkers, New York. Read more on Wikipedia.
Wikidata - #6 Päijänne Water Tunnel — 120 km
120-kilometre water tunnel in Southern Finland
The Päijänne Water Tunnel is a water tunnel located in Southern Finland. At 120 kilometers (75 mi), it is the second-longest tunnel in the world, running at a depth of 30–100 metres (100–330 ft) in the bedrock. Read more on Wikipedia.
Wikidata - #7 Orange–Fish River Tunnel — 83 km
Irrigation tunnel in South Africa
The Orange–Fish Tunnel, constructed between 1966 and 1975, is an 82.8-kilometre-long (51.4-mile) irrigation tunnel in central South Africa, built to divert water from the Orange River to the Fish River valley. It is the longest continuous enclosed aqueduct in the southern hemisphere. Read more on Wikipedia.
Wikidata - #8 Zarch Qanat — 80 km
qanat in Yazd County, Iranian national heritage site and World heritage site
source Wikidata - #9 Ishikawa Tunnel — 79 km
part of Japan National Route 329 in Uruma, Okinawa
The Ishikawa Tunnel is part of Japan National Route 329 in Uruma, Okinawa. It cuts through the cliffs south of Ishikawa to connect the Ishikawa By-pass to Route 329 proper. The by-pass, tunnel, and bridge were built in the 1990s. Read more on Wikipedia.
Wikidata - #10 Brenner Base Tunnel — 64 km
railway tunnel
The Brenner Base Tunnel is a 55-kilometre-long (34 mi) railway tunnel under construction through the base of the Eastern Alps beneath the Brenner Pass. Once completed, the Brenner Base Tunnel will rank as either the second or third longest railway tunnel in the world, depending on the definition employed. It will be surpassed in length only by the Gotthard Base Tunnel in Switzerland and, depending on the relative completion dates of these projects, the Mont d'Ambin Base Tunnel between France... Read more on Wikipedia.
Wikidata