The France international defender, who has played all across the back line for the Magpies, goes to Serie A for an initial £1 million fee with an option to buy for £5.5m
The Serie A club also have the option to purchase the 25-year-old for £5.5m.
The France international joined Alan Pardew's side in January 2013 and has played nearly 50 games for the club, though had yet to feature in 2014-15.
He rose through the ranks at Montpellier, playing over 130 league games for the club and winning Ligue 1 in 2011-12.
Newcastle are also set to lose Hatem Ben Arfa on transfer deadline day, with Goal revealing that the Magpies outcast close to a loan deal with Hull City.