Iran has discovered a new oil field in the country's south with an estimated 50 billion barrels of crude oil, its president said.
The find could boost the country's proven reserves by a third as it struggles to sell energy abroad amid US sanctions.
The announcement by Hassan Rouhani comes as Iran faces crushing American sanctions after the US pulled out of its nuclear deal with world powers last year.
Mr Rouhani made the announcement in a speech in the desert city of Yazd. He said the field was located in Iran's southern Khuzestan province, home to its crucial oil industry.
He added that 50 billion barrels would be added to Iran's proven reserves of some 150 billion.
Proven reserves are those that are commercially feasible to extract.
The new oil field could become Iran's second-largest field after one containing 65 billion barrels in Ahvaz.