Erdoğan said the 320-billion-cubic-metre deep sea find was made at a site Turkish vessel Fatih began exploring last month.
He added that he hoped to see the first gas reach Turkish consumers in 2023, the 100th anniversary of the birth of the modern republic.
"Turkey made the biggest discovery of natural gas in its history in the Black Sea," a delighted Erdoğan said during a speech in Istanbul's Dolmabahçe Palace.
"My Lord has opened the door to unprecedented wealth for us," he enthused.