Two Spanish military planes carrying 17 tonnes of silver and gold coins have left the United States for Spain after a five year legal battle. They carried 594,000 coins and other artefacts.
The BBC reports the coins were recovered from a Spanish galleon that was sunk by the English near the Straits of Gibraltar in 1804.
Odyssey Marine Exploration found the coins in a wreck off Portugal's Atlantic coast in 2007.
At the time, the treasure was estimated to be worth $US500 million.
The wreck is believed to have been that of the Nuestra Senora de las Mercedes, which was sunk by a British warship in 1804.
However, the Spanish government began legal proceedings against Odyssey to recover the coins.
Odyssey argued in court that the wreck was never positively identified as the Mercedes.
Spain countered that it had never relinquished ownership of the cargo.
A federal judge recently issued a final ruling against Odyssey. The BBC reports the coins will be exhibited in museums in Spain.