The 19-year-old has joined the BLues on a five-and-a-half year contract.
Chelsea announced in a statement today:
“Chelsea Football Club has today (Friday) signed Kurt Zouma from St. Etienne. He will remain on loan at the French club for the rest of the season.
“The 19-year-old central defender has joined Chelsea on a five-and-a-half year contract. This season he has made 12 league appearances for France’s fourth-placed side.
“The 6ft 2in Zouma is a French Under-21 international. He was born in Lyon and joined St. Etienne as a 15-year-old in 2009, turning professional in 2011. In total he has made 52 league appearances for ‘Les Verts’ and scored four goals.”