"I am so happy to have signed for one of the biggest clubs in Europe. It’s a dream come true for me," the midfielder told .
"The opportunity to work with , a brilliant coach, and some of the best players in the world was simply too good to turn down."
The 25-year-old is the second signing of new manager Conte following Olympique Marseille's Belgium striker Michy Batshuayi, who arrived after playing at Euro 2016.
Kante was Claudio Ranieri's first signing at Leicester, joining for six million pounds after two seasons at Caen.
Kante played in all but one of Leicester's league games and made most overall tackles and interceptions in the competition.
His efforts saw him named in the PFA Team of the Year.
Chelsea technical director Michael Emenalo said: "N’Golo is a fantastic signing. He is a perfect fit in terms of Antonio Conte’s philosophies and the style of football he wants to play.
"For a player of his age he has already built up a wealth of experience and his exceptional quality will without doubt be a great addition to the team.".