The largest fjord system in the world is Scoresby Sund (Kangertittivaq) in eastern Greenland, which branches inland for about 350 km and reaches depths of around 1,450 m. The longest fjord in Norway, often described as the second-longest in the world, is the Sognefjord, at 205 km long and 1,308 m deep.
Fjords can be ranked by length, depth or area, and different fjords lead in each. Greenland wins on size, Norway on fame, and Antarctica on depth, while Chile, New Zealand, Canada and Alaska hold thousands more along their glaciated coasts. What unites them is ice: every true fjord is a valley deepened by a glacier and then invaded by the sea.
What Turns a Glacial Valley Into a Fjord
During ice ages, glaciers flowing from mountain ice caps to the coast follow existing river valleys and grind them into deep, U-shaped troughs with steep walls. Because a thick glacier keeps eroding as long as it rests on its bed, it can carve far below sea level — often much deeper in the middle of the fjord than at its mouth. Where the glacier spread out and thinned as it reached the open sea, it eroded less and dropped rubble, leaving a shallow ridge called a sill across the entrance.
When the ice melted at the end of the last glaciation, roughly 10,000 to 20,000 years ago depending on the region, rising seas flooded these troughs. The result is a long, narrow arm of the sea, often deeper than the ocean just offshore, with walls that can rise more than 1,000 m almost vertically from the water. The sill restricts circulation, so the deep water in some fjords is renewed only occasionally.
The word comes from Old Norse fjǫrðr, a place to cross, and shares its root with the English "ford" and the Scots "firth." In New Zealand it is spelled "fiord."
Measured by Length: The Longest Fjords
Length rankings for Greenland are approximate because its fjords branch extensively and many were mapped only in the twentieth century. Norway's figures, by contrast, are measured precisely, and the Sognefjord's 205 km is the benchmark most other fjords are compared against.
Scoresby Sund: Greenland's 350-Kilometre Maze
Scoresby Sund opens onto the Greenland Sea on Greenland's east coast at about 70° N. Its broad main basin leads inland to a network of branches — Nordvestfjord, Øfjord, Rødefjord and others — that wind between mountains rising more than 2,000 m. Following the longest arm, Nordvestfjord, the system extends about 350 km from the open sea to the margin of the Greenland Ice Sheet. Its total area, often quoted at around 38,000 km², is larger than Belgium.
The fjord is named after the English whaler and scientist William Scoresby Jr., who charted its entrance in 1822. Its Greenlandic name, Kangertittivaq, means "the large fjord." The only town, Ittoqqortoormiit, was founded near the mouth in 1925 and is home to a few hundred people, who hunt seals, narwhals and musk oxen. The fjord is ice-covered for around nine months a year, and outlet glaciers such as the Daugaard-Jensen Glacier fill its inner branches with icebergs, some of which run aground on the sill.
Norway's Western Fjords
Sognefjord
Running inland from the coast north of Bergen to Skjolden, the Sognefjord is 205 km long and reaches 1,308 m deep, while its entrance sill is only around 100–200 m deep. Mountains along its inner reaches rise over 1,000 m, and its branches include the Nærøyfjord, roughly 17 km long and only about 250 m wide at its narrowest, and the Aurlandsfjord, where the steep Flåm Railway descends to the water.
Hardangerfjord
The Hardangerfjord, 179 km long and up to about 890 m deep, runs south-east of Bergen beneath the Folgefonna ice cap. Its sheltered slopes are known for apple and cherry orchards that blossom in May, and Trolltunga, the famous rock ledge, overhangs a lake above the town of Odda at the head of its Sørfjord branch. The Hardanger Bridge, opened in 2013, crosses one of its arms with a main span of 1,310 m.
Geirangerfjord and Nærøyfjord
Two smaller fjords became Norway's most famous: the Geirangerfjord, about 15 km long and known for waterfalls such as the Seven Sisters, and the Nærøyfjord. Together they were inscribed by UNESCO in 2005 as the West Norwegian Fjords. Their steep walls carry risks: geologists monitor the unstable Åkerneset mountainside above the nearby Sunnylvsfjord because a collapse could send a tsunami toward Geiranger and Hellesylt.
Living on the Fjords: Ferries, Tunnels and Salmon
Norway's fjords are unusual among the world's large fjords because they never freeze. The North Atlantic Current, an extension of the Gulf Stream, keeps the coast far milder than its latitude suggests, so the Sognefjord lies at the same latitude as southern Greenland yet stays open to shipping all year. That warmth allowed farming and settlement deep inland: small farms cling to ledges hundreds of metres above the water, some of them, like Skageflå above the Geirangerfjord, reached historically only by steep paths and ladders.
For travel, fjords are barriers as much as routes. Western Norway's main roads have long depended on car ferries, and the country has spent decades replacing them with bridges and tunnels. The 24.5 km Lærdal Tunnel, opened in 2000 on the route between Oslo and Bergen near the Sognefjord, is the longest road tunnel in the world. The sheltered, deep, well-oxygenated water also made Norway's fjords and coast the centre of the world's largest Atlantic salmon farming industry, which brings both export revenue and concerns about sea lice and escaped fish affecting wild salmon.
Tourism is the newest pressure. Cruise ships crowd the narrow arms of Geiranger and Nærøy in summer, and Norway has legislated to phase in zero-emission requirements for ships entering its World Heritage fjords, starting in 2026.
Greenland's fjords support a very different life. Kangerlussuaq Fjord on the west coast, about 190 km long, ends at the settlement of Kangerlussuaq, whose former US airbase served for decades as Greenland's main international airport because the fjord head's dry, stable inland weather made it reliable for flying — a role largely passed to Nuuk after its longer runway opened in 2024. Elsewhere in Greenland, fjords serve as hunting grounds and travel routes over winter sea ice.
Ice, Depth and Rain: Fjords Beyond Norway
- Ilulissat Icefjord, Greenland. Fed by Sermeq Kujalleq (Jakobshavn Glacier), one of the fastest and most productive glaciers in the world, this fjord is packed with icebergs. It became a UNESCO World Heritage Site in 2004.
- Skelton Inlet, Antarctica. Often cited as the deepest fjord known, at about 1,900 m.
- Patagonian fjords, Chile. Chile's southern coast dissolves into thousands of islands and fjords; the Messier Channel reaches nearly 1,300 m deep.
- Fiordland, New Zealand. Fourteen fiords cut the south-west of the South Island. Milford Sound (Piopiotahi), only about 15 km long, receives roughly 6–7 m of rain a year, with Mitre Peak rising 1,692 m above the water.
- Canada and Alaska. British Columbia's coast is lined with long inlets such as Knight Inlet, while Baffin Island has fjords with some of the tallest rock walls on Earth.
Fjord, Ria or Sound? How They Differ
Coastal inlets often get names that do not match their origins, so it is worth separating three landforms:
- Fjord. A glacier-carved, U-shaped trough, usually with a shallow sill at the mouth and the greatest depth well inland. Examples: Sognefjord, Scoresby Sund.
- Ria. A river valley drowned by rising seas, never shaped by ice. It is V-shaped in cross-section and gets steadily deeper toward the sea, with no sill. The word comes from Galicia in north-west Spain, whose Rías Baixas are classic examples; Chesapeake Bay is a much larger drowned river valley.
- Sound. A loose name for an inlet or a channel between land masses that says nothing about its origin. Milford Sound is in fact a fjord; Puget Sound in Washington State is a glacially carved system; Long Island Sound is something else again.
The difference matters for more than labels. Fjords' deep basins and sills trap cold, still water and create unusual habitats, such as deep-water coral reefs in Norway at depths where they would normally be found far offshore, while rias, with their shallow, gently sloping beds, typically make productive estuaries and natural harbours.
To plan a trip around the longest of them, read our Sognefjorden guide, or the Geirangerfjord guide for the most visited. For the science of how they form, see what is a fjord, and to understand the ice that feeds Greenland's giants, explore the Greenland Ice Sheet guide.