The Greek oil tanker Prestige splits in half and sinks off the coast of Galicia, releasing over 20 million US gallons (76,000 m³) of oil in the largest environmental disaster in Spanish and Portuguese history.

The Prestige oil spill occurred off the coast of Galicia, Spain, caused by the sinking of the 26 year old structurally deficient oil tanker MV Prestige in November 2002, carrying 77,000 tonnes of heavy fuel oil. During a storm, it burst a tank on November 13, and French, Spanish, and Portuguese governments refused to allow the ship to dock. The vessel subsequently sank on November 19, 2002, about 210 kilometres (130 mi) from the coast of Galicia. It is estimated that it spilled 60,000 tonnes or a volume of 67,000 m3 (17.8 million US gal) of heavy fuel oil.

The spill polluted thousands of kilometers of coastline and more than one thousand beaches on the Spanish, French and Portuguese coast, as well as causing great harm to the local fishing industry. The spill is the largest environmental disaster in the history of both Spain and Portugal. The amount of oil spilled was more than the Exxon Valdez incident and the toxicity considered higher, because of the higher water temperatures.

In 2007 the Southern District of New York dismissed a 2003 lawsuit by the Kingdom of Spain against the American Bureau of Shipping, the international classification society which had certified the Prestige as in compliance with rules and laws, because ABS was a "person" per the International Convention on Civil Liability for Oil Pollution Damage and exempt from direct liability for pollution damage. The 2012 trial of the Galicia regional High Court did not find the merchant shipping company, nor the insurer, the London P&I Club nor any Spanish government official, but only the Captain of the ship guilty and gave him a nine-month suspended sentence for disobedience. In January 2016 the Spanish Supreme Court held the London P&I Club liable in damages up to the amount of its overall cover for the shipowner for pollution of $1 billion. The Spanish judgment is unlikely to be enforceable due to a UK judgment requiring any claims to be determined via arbitration under UK law. The overall damages awarded by the court in A Corua in 2017 was just over 1.5bn, a figure confirmed by the Spanish Supreme Court in December 2018.

An oil tanker, also known as a petroleum tanker, is a ship designed for the bulk transport of oil or its products. There are two basic types of oil tankers: crude tankers and product tankers. Crude tankers move large quantities of unrefined crude oil from its point of extraction to refineries. Product tankers, generally much smaller, are designed to move refined products from refineries to points near consuming markets.

Oil tankers are often classified by their size as well as their occupation. The size classes range from inland or coastal tankers of a few thousand metric tons of deadweight (DWT) to the mammoth ultra large crude carriers (ULCCs) of 550,000 DWT. Tankers move approximately 2.0 billion metric tons (2.2 billion short tons) of oil every year. Second only to pipelines in terms of efficiency, the average cost of transport of crude oil by tanker amounts to only US$5 to $8 per cubic metre ($0.02 to $0.03 per US gallon).Some specialized types of oil tankers have evolved. One of these is the naval replenishment oiler, a tanker which can fuel a moving vessel. Combination ore-bulk-oil carriers and permanently moored floating storage units are two other variations on the standard oil tanker design. Oil tankers have been involved in a number of damaging and high-profile oil spills. As a result, they are subject to stringent design and operational regulations.