Insights · Data · Largest oil tankers
One ship dwarfs every other tanker that has ever floated. The Seawise Giant was so large that no port on earth could take it fully laden — and nothing built since has come close. Here is how tankers are measured, why the record still stands, and what the largest tankers afloat today actually carry.
The largest oil tanker ever built was the Seawise Giant: 564,763 deadweight tonnes and 458.45 metres in length overall (figure stable as of June 2026). That is not just a tanker record — it makes the Seawise Giant the largest self-propelled ship of any type ever constructed. Fully laden she displaced more than 650,000 tonnes of water, a mass that no vessel before or since has matched under its own power.
To understand why that number still stands — and why nothing remotely as large sails today — it helps to start with how tankers are measured and sorted in the first place.
Crude tankers are ranked by deadweight tonnage (DWT): the total mass of cargo, fuel, stores, water and crew a ship can carry when loaded to her marks. It is the figure that matters commercially, because for a tanker it is essentially a measure of how much oil she can move. Note that DWT is a measure of carrying capacity, not the same thing as gross tonnage, which describes a ship's enclosed volume.
By deadweight, crude tankers fall into a handful of recognised size classes:
You can see the whole class spread for yourself by filtering the tanker fleet in the Marifest registry and sorting by deadweight — the VLCCs cluster near the top, with very little above them.
The Seawise Giant was built in 1979 by Sumitomo Heavy Industries in Japan. Over a long and turbulent career she carried several names — at various points she was the Happy Giant, the Jahre Viking and the Knock Nevis — which is itself a neat illustration of why a permanent identifier matters more than a paint job.
Her life was not a quiet one. During the Iran–Iraq war she was attacked and badly damaged, sinking in shallow water in the Persian Gulf. She was later salvaged, extensively repaired and returned to service — a remarkable second act for a hull of that size. She finished her days not as a trading tanker but as a permanently moored floating storage and offloading unit, before finally being beached at Alang, India, where her scrapping was completed in 2010.
At 458.45 metres and 564,763 deadweight tonnes, the Seawise Giant was longer than the Empire State Building is tall — and no tanker built since has come within a third of a million tonnes of her. Seawise Giant, ex Happy Giant / Jahre Viking / Knock Nevis
The obvious question is why, decades on, nobody has built a tanker to beat her. The answer is not that it cannot be done. It is that it makes no commercial sense.
A ship the size of the Seawise Giant has an enormous laden draught — the depth of hull below the waterline — and that immediately rules out the great majority of the world's ports, which simply cannot accommodate her. She was also far too large to transit the Suez Canal, forcing the long route around the Cape of Good Hope. Build a ship that can only be loaded and discharged at a tiny handful of deep-water terminals and you have built something inflexible and expensive to route.
The ULCC giants made sense for a brief window in the 1970s, when very long crude hauls and high oil prices rewarded sheer scale. Once the oil shocks of that decade faded, the economics reversed, and the class effectively died out. The market settled on the VLCC — large enough for economies of scale, small enough to call at far more terminals — as the practical ceiling. So the reason no ULCC the size of the Seawise Giant exists today is commercial and physical, not technical.
That leaves the VLCC as the giant of the modern tanker world. These ships carry roughly 300,000–320,000 DWT — around half the deadweight of the Seawise Giant — and they form the backbone of long-haul crude transport between the Gulf, Asia and the West. They are still vast: a loaded VLCC is one of the largest moving objects most people will never see.
If you want to explore the class directly, you can look up the tanker sector on Marifest and read individual vessel files — deadweight, dimensions, ownership chain, flag history and sanctions standing — all anchored to each ship's permanent identifier. To put a given vessel's size in context, the maritime glossary explains the class thresholds, and our wider look at ship types explained sets tankers alongside the rest of the merchant fleet.
For all the modern fleet's scale, the headline number has not changed in nearly half a century. The Seawise Giant remains the largest oil tanker ever built — a record that, for sound commercial reasons, is unlikely ever to be broken. You can search the tanker fleet in the Marifest registry to see exactly where today's giants stop short.
How Marifest uses it
Marifest keeps the full tanker fleet in one open registry, each ship filed by deadweight, size class and permanent identifier. That makes it easy to see where the modern VLCCs top out — and to find the historic giants that no port could load.
Open the registry's tanker sector and sort by deadweight to see Aframax, Suezmax and VLCC hulls line up — with the VLCCs clustered near the top of the fleet.
Every tanker file records its DWT, so you can compare carrying capacity ship for ship and place any vessel in its proper size class.
The glossary defines Aframax, Suezmax, VLCC and ULCC thresholds, so the number on a vessel file always means something concrete.
Ships like the Seawise Giant carried many names over their life. Marifest keys each record to a permanent identifier, so the history follows the hull.