The 66-year-old former Italy coach has signed a two-year contract with Stuttgart, the club said on Friday. It will be his third spell in Germany, after twice being in charge at Bayern Munich.
Trapattoni stepped down as Benfica coach at the end of May after steering them to their first Portuguese championship in 11 years.
He said then that he wanted to return to Italy to be with his family and his biggest task was convincing his wife that it was the right move for them, Stuttgart said.
The city, in southern Germany, is at least a manageable drive to the Italian border.
Trapattoni brings with him a phenomenal record of success.
The Portuguese championship was his ninth league title in a long career with several European clubs,
As a defender with AC Milan he won European Cup winners' medals in 1963 and 1969.
His coaching career has taken him to AC and Inter Milan, Juventus, Fiorentina, Cagliari and Bayern Munich. His first spell in Munich ended after just one season in 1995 with complaints that he had difficulty with the language.
He returned a year later, however, and led Bayern to the German title.
He was appointed Italy manager in 2000, but the side failed to sparkle under his charge, eliminated by South Korea in the second round of the 2002 World Cup and failing to get past the group stage in Euro 2004.
Sammer left Stuttgart after just one season at the club following a dismal run of form that cost them a place in the Champions League.