The deal, signed during a visit to Tripoli by Italy's Prime Minister Giorgia Meloni, aims to increase gas output for the Libyan domestic market as well as exports, through the development of two offshore gas fields.
Output will begin in 2026 and reach a plateau of 750 million cubic feet per day, Eni said in a statement.
"This agreement will enable important investments in Libya's energy sector, contributing to local development and job creation while strengthening Eni's role as a leading operator in the country," said its chief executive, Claudio Descalzi.
Meloni met Libya's Prime Minister Abdulhamid al-Dbeibah, head of the internationally recognised Government of National Unity (GNU) in Tripoli for talks that also focused on migration across the Mediterranean.
Italian Interior Minister Matteo Piantedosi, who oversees the migration issue for Rome, accompanied Meloni to Libya, as well as Foreign Minister Antonio Tajani.