Rudi Garcia has agreed a three-year deal to take over at Marseille, on the same day his Roma contract was terminated by mutual consent.
The 52-year-old left the Serie A outfit in January, having taken the role in 2013.
But it was not until Thursday that he was formally released from the club, along with his assistants.
The Frenchman wasted little time in agreeing a move to his homeland, where he takes the helm at a Marseille side residing in 12th.
But he has high hopes for the future, with owner Frank McCourt outlining the ambition that helped land Garcia the position.
"When I met Rudi he immediately told me he wanted to win the Champions League," he said. "I immediately knew he was the man for the job.
"Rudi is a man of great character with lots of energy and we share the same vision for OM and a similar determination to implement it.
"His leadership skills have been recognised on several occasions: when he led Lille to victory in Ligue 1 and the Coupe de France in 2010-11; when he led Roma to play a leading role on the international stage during his first two seasons with the club; or, when he won the French title of Coach of the Year in 2011, 2013 and 2014.
"Rudi knows what it takes for a team to lead to victory and he is used to playing the first roles. Like all OM players, the fans, and the entire city of Marseille, I am looking forward to our future success."
His first task is a sizeable one, as he takes his new charges to French champions Paris Saint-Germain on Sunday.
Marseille's statement did not comment on the status of previous interim boss Franck Passi.
