The arrival of Giampaolo is the first major decision made by the new backroom duo of Paolo Maldini and Zvonimir Boban, Milan's new technical director and chief football officer respectively.
Giampaolo led Sampdoria to ninth-place last season having previously coached Empoli, Brescia and Cagliari.
AC Milan, seven-time champions of Europe, have not played in the Champions League since 2013-14.
Having grown impatient with his former club's unwillingness to push on and spend money in the transfer market, I Rossoneri now provide the flawless platform for the 51-year-old to hone his skills as a football manager.
Avalanche strands 4 Italian, 3 local climbers
The four Italian climbers involved are expedition leader Tarcisio Bellò, Luca Morellato, David Bergamin and Tino Toldo. The club said in a statement on Tuesday that the Pakistani Army is delivering a helicopter to rescue the climbers.
Shakib Al Hasan, Australia face resurgent Bangladesh
Mahmudullah has been hot and cold in the tournament and he would like to show his worth against a top side like Australia . In-form all-rounder Shakib al Hasan is now the highest run-scorer at the World Cup 2019 with 384 runs in four innings.