it is believed the 20-year-old Belgium international is set for a medical ahead of signing a five-year contract.
He is likely to be in the stands at Goodison Park to watch Saturday's home game against Chelsea.
Onana will provide a much-needed option in midfield, an area manager Frank Lampard is looking to strengthen further with a deal to bring former Toffees player Idrissa Gana Gueye back from Paris Saint-Germain.
West Ham were also interested in Onana but Everton have beaten their Premier League rivals to his signature.
The 20-year-old arrived in Ligue 1 from Hamburger SV and made 43 appearances for the club across all competitions.
The player signed a five-year deal with Lille, meaning his contract expires in the summer of 2026.
Onana has Champions League football under his belt, having featured for the Mastiffs against Chelsea in the round-of-16 last season.
The youngster made his senior international debut back in June. Onana took part in a Nations League clash against the Netherlands after impressing manager Roberto Martinez.