Eni has made the tenth commercial oil discovery at the deepwater Ochigufu exploration prospect in Block 15/06 offshore Angola.
The company estimates the new discovery holds 300 million barrels of oil in place.
Eni said it will bring the Ochigufu 1 NFW well, which led to the discovery, into production in record time.
The well, located about 150km off the coast of Angola, was drilled by the Ocean Rig Poseidon drilling unit in a water depth of 1,337m and reached a total depth of 4,470m.
Eni CEO Claudio Descalzi said: "This important discovery, which will be brought into production in record time, adds even more value to Block 15/06.
"Like the recent discoveries in Congo and Gabon, this new find exemplifies the results we can achieve by applying leading edge technologies to exploration and substantiates the decision to refocus Eni on key oil and gas competences."
Eni operates the Block 15/06 with a 35% stake while Sonangol P&P and SSI Fifteen hold 30% and 25% stakes respectively; Falcon Oil Holding Angola and Statoil Angola each hold 5% stakes in the block.
Eni started operations in Angola in 1980 and the company produced approximately 90,000 barrels of oil equivalent per day in 2013.
The two oil development projects, West Hub and East Hub, in Block 15/06 have already been approved.
The West Hub project production start up, via FPSO Ngoma, is planned to commence by the end of this year.
Eni also operates Block 35, which is situated in the deepwater Kwanza Basin, Angola.