Conte's move to Stamford Bridge was announced in April and he will take over when his Italy contract expires at the end of this summer's tournament.
Ventura, 68, most recently coached Serie A side Torino and led them to 12th in the league last season.
His five-year tenure at the club - including promotion from Serie B in his first year - came to an end in May.
Ventura's only managerial trophy is a third division title with Lecce in 1996, but Italian football federation president Carlo Tavecchio described him as a "master of football".
Tavecchio also called Ventura an "innovative" coach with "limitless experience" who has helped many players reach the national side.
He will have a two-year deal until the end of the Russia 2018 World Cup and is expected to take several of his key staff from Torino to the Italy set-up.
Conte announced in March that he would step down as Italy coach after Euro 2016.
Italy face Belgium, Sweden and Ireland in Group E.
Italy will replace Chelsea-bound national coach Antonio Conte with Giampiero Ventura after Euro 2016.