The Foxes are expected to pay more than £30million (€33 million) for the 19-year-old, with the Ligue 1 side confirming it would be a club record sale.
It will end Leicester’s interest in Burnley’s James Tarkowski, who had been keen on a move to the King Power Stadium, after they had a bid worth more than £30million rejected last week.
A St Etienne statement read: “AS Saint-Etienne reached an agreement on Tuesday evening with Leicester, the current leaders of the English Premier League, for the transfer of defender Wesley Fofana.
“The amount of this transfer is the largest ever obtained by the club.”
The amount of this transfer is the largest ever obtained by the club
Boss Brendan Rodgers had targeted a new centre-back and Fofana had spoken out about wanting to move to the Midlands after an initial bid was turned down earlier this month.
“I’ve received a lot of offers,” Fofana told L’Equipe. “It’s normal to have them checked with my agents. They didn’t agree to me talking. But what just happened broke something in me.
“My decision is made: I accept an offer. Yes (to Leicester). I’ve always dreamed of playing in England.”
Leicester had also been chasing Tarkowski and had two bids rejected in January in addition to last week’s offer.
Burnley had also turned down two approaches from West Ham with their valuation closer to £40million.
The Clarets were confident of keeping the England international and never entertained selling him.
Leicester have already signed Timothy Castagne from Atalanta for £21.5million and Cengiz Under on loan from Roma.
