Billionaire Iranian businessman Babak Zanjani has been sentenced to death for corruption, justice officials say.
He was arrested in December 2013 after accusations that he withheld billions in oil revenue channelled through his companies. He denies the allegations.
Zanjani, 42, was convicted of fraud and economic crimes, a judiciary spokesperson said at a press briefing.
One of Iran's richest men, Zanjani was blacklisted by the US and EU for helping Iran evade oil sanctions.
Two others were sentenced to death along with him and all were ordered to repay embezzled funds. The ruling can be appealed.
In a separate development, a cargo of Iranian crude oil arrived at a Spanish refinery in San Roque on Sunday, the first delivery to an EU state since sanctions were lifted.
The Monte Toledo offloaded 1m barrels at the refinery belonging to Spanish oil company Cepsa.
Before the oil embargo imposed by the EU in 2012, one in every five barrels of crude Iran exported was sold to refineries in Europe.
'Just a debtor'
Zohreh Rezalee, a lawyer for Zanjani, told the BBC the verdict was politically motivated and an appeal would be lodged.
"We believe that Babak Zanjani in this case is just a debtor," the lawyer said.
Who is Babak Zanjani?
- Played a key role in helping Iran get around sanctions to sell oil abroad during the presidency of Mahmoud Ahmadinejad
- From Dubai, he controlled a global network of more than 60 companies involved in everything from cosmetics to air travel and banking
- Accused of impropriety after Hassan Rouhani, a moderate who pledged to tackle high-level corruption, became president in 2013
- Born in Tehran, attended a Turkish university and became a driver for Iran's central bank head in 1999, when he started out in currency exchange
- Said he was worth $13.5bn but was reported to have significant debts
Zanjani had acknowledged using a web of companies in the United Arab Emirates, Turkey, and Malaysia to sell millions of barrels of Iranian oil on behalf of the government since 2010.
Before his arrest, Zanjani had argued that international sanctions were preventing him from handing over $1.2bn still owed to the government.
But at his recent trial, prosecutors said he still owed the government more than $2.7bn in oil revenue.
He was taken into custody a day after President Hassan Rouhani ordered his government to fight "financial corruption", particularly "privileged figures" who had "taken advantage of economic sanctions" under the previous government.
The trial, unusually, was held in public, AFP news agency reports.
In a 2013 interview with the BBC, Zanjani played down his political connections in Iran, saying: "I don't do anything political, I just do business."
Zanjani has said he is worth about some $13.5bn.
For years things worked well for the businessman who appeared in photos with some high-ranking officials and was not shy of showing off his wealth, such as private jets and luxury cars, Amir Azimi of BBC Persian reports.
But when the local media started to report on his wealth, he came under the spotlight and under suspicion.
The death sentence could have wider implications for Iran's economy, where many were involved in finding ways to avoid the sanctions, our analyst adds.
International sanctions on Iran were lifted in January after a watchdog confirmed it had complied with a deal designed to prevent it developing nuclear weapons.
Oil minister Bijan Zanganeh has urged foreign investors to avoid middlemen, whom he describes as "corrupt parasites".
Zanjani was convicted of "corruption on earth", the most serious offence in Iran's criminal code.
Other wealthy individuals have been executed after being found guilty of similar charges.
In May 2014, businessman Mahafarid Amir-Khosravi was hanged after being convicted of embezzling billions of dollars.